As an education reform, the broad goal of class size reduction (CSR) is to increase the number of individualized student-teacher interactions intended to improve student learning. A reform long holding theoretical attraction to many constituencies, some have claimed CSR as the most studied educational reform of the last century. Until recently, interpretations of these studies has often been contentious. Some educational groups like the American Federation of Teachers and National Education Association are in favor of reducing class sizes. Others argue that class size reduction has little effect on student achievement. Many are concerned about the costs of reducing class sizes.
Elizabeth Garue, the primary researcher on Project SAGE, says, “There are indeed significant effects on student achievement related to reduced class sizes, but the effort itself does not guarantee success without additional attention to teacher quality, increased funding, availability of necessary facilities, and community/district belief in the power of the reform." Studies following the work of Project Star and Sage found that, even when reintroduced to larger class-sizes later in their educational career, the positive foundation for learning caused students to later in life to be more likely to take advanced classes and attend college.
Subsequent research has confirmed that smaller classes beneﬁt all pupils because of individual attention from teachers, but low-attaining pupils beneﬁt more at the secondary school level. Pupils in large classes drift off task because of too much instruction from the teacher to the whole class instead of individual attention, and low-attaining students are most affected. Students beneﬁt in later grades from being in small classes during early grades. Longer periods in small classes resulted in more increases in achievement in later grades for all students. In reading and science, low achievers beneﬁt more from being in small classes. The beneﬁts of small class sizes reduce the student achievement gap in reading and science in later grades.
- 1 Effects
- 2 Definition of class size
- 3 Modern research and studies
- 4 Difficulties of implementation in California
- 5 Teacher training
- 6 Measuring the effects of reduced class sizes
- 7 Economics of smaller classrooms
- 8 References
- 9 External links
In recent years, in the aftermath of Project STAR and Project SAGE, there is evidence validating the perceived benefits of class-size reduction, especially in its ability to narrow the achievement gap for minorities. Today, more than 30 states have enacted class size reduction legislation as a way to “lessen the effects of economic and social inequities, to increase academic achievement, and to strengthen the foundational social skills students develop in primary grades” 
Studies finding statistically significant benefits from class size reduction show more positive teacher-student interactions leading to less time spent on discipline, the increased use of balanced instructional methods including higher degrees of individualization, closer personal relationships for teachers with students and families, a decrease in the effects of economic and social inequalities, increased student achievement, and establishment of a stronger foundation for lifelong learning beginning in the primary grades.
McEwan and McEwan evaluated the results in 2003 und inferred that a small class can be viewed as a necessary but not sufficient condition for improving achievement; class size reduction ‘works’, but only to the extent that it leads to improved instruction.
Definition of class size
An early complication in measuring the efficacy of class size reduction was the tendency for different ideological camps to use different definitions of class size in the literature. As a direct measure of the number of students in each class, group size is currently understood by the educational community to be the best measure of a teacher's "true opportunity to build direct relationships with each student." A more malleable definition and one now held in dubious regard, pupil to teacher ratio, would declare a situation in which one teacher leads a class while another does paperwork in the back but does not interact with students as being half as large as its group size.
In the past, depending on which measure was used, researchers tended toward far different interpretations of the benefits of class size reduction leading to far different recommendations for implementation. In 2002, Margaret Spellings, secretary of education under President George W. Bush, pointed out the need for a standardized definition of what is meant by class size.
To differentiate student-teacher ratio and class size, it is important to know several key distinctions. Class size, generally speaking, refers to the average class size in a given grade level of a given school. Student-teacher ratios, normally, are calculated by taking the total number of teachers at a given school divided by the complete enrollment of that school. This distinction is significant, because the ratio will not always match up with the class size figure (or vice versa). For example, a student-teacher ratio may be small but a class size may be larger than what the student-teacher ratio leads one to believe.
Modern research and studies
Project Prime Time
In 1986 the state of Indiana initiated Project Prime Time.
(1) Students in smaller class sizes scored higher on standardized tests
(2) Smaller classes had fewer behavioral issues
(3) Teachers of smaller class sizes reported themselves as more productive and efficient
Also In 2001 The "No Child Left Behind" was introduced.
Aware of both the preliminary results of Project Prime Time in Indiana and the potential large scale costs of additional classrooms and teachers, in 1985, under then Governor Lamar Alexander, Tennessee began a three-phase project to determine the effects of reduced class sizes on short and long term pupil performance in the earliest grades.
The first phase, termed Project STAR (Student-Teacher Achievement ratio), randomly assigned teachers and students to three groups, “small” (13 to 17), “regular” (22 to 25) classes with a paid aide, and “regular” (22 to 25) classes with no aide. In total some 6,500 students in about 330 classrooms at approximately 80 schools participated.
Using both standardized and curriculum based testing, the initial study concluded that small classes produced “substantial improvement in early learning and cognitive studies” with the effect about double for minority students. As this is considered the seminal study (in an area that has received much political attention) there have been many attempts to reinterpret the data.
Dubbed the Lasting Benefits Study, the second phase began in 1989 and sought to determine whether the benefits of CSR persisted into upper grades when all students entered standard size classes. Observations confirmed that children originally enrolled in smaller classes continued to outperform their peers when they returned to regular-sized classrooms. These results were deemed true for all types of classes and all types of cities (rural, suburban, and metropolitan).
Under the third phase, Project Challenge, the 17 economically poorest school districts were adequately funded to provide smaller class sizes for their K-3 students. These districts improved their end-of-year- standing (among 139 districts) in mathematics and reading from below average to above average.
However, Dr. Eric Hanushek, then of Rochester University, called into question the validity of the study on Project Star, noting not only that the bulk of scientific research on small-class sizes shows no or statistically insignificant effects, but that Project STAR produced an achievement gain that was apparent in only the first year. If small class sizes produced better student achievement, the gains should be cumulative, that is, improve from year to year. Dr. Hanushek reasoned that there must be another explanation, like flawed random assignment, that produced the result rather than small class size.
Lessons from Project STAR
Despite protests from several of the originating legislators, teacher training consisted solely of a three day course. Given that most teachers are trained to teach in large classrooms, subsequent studies have also highlighted the importance of personal development to successful implementation of CSR.
Although a large mix of socioeconomic students and school districts were represented it should be noted that some of lowest income schools couldn’t participate in the study because they lacked funds to comply with the class size requirement.
In 2002 the state of Wisconsin began its own investigations into “the wisdom of class size reduction."  In all, nine low income schools were studied, their locations spanning urban, semi-urban, and rural geographies. Evaluation included site visits, standardized assessments, collection of curriculum, and interviews with teachers, principals, and students.
The guiding assumptions of the study were:
(1) Class size implementation alone is insufficient to promote student achievement. Changes in teaching methods that take full advantage of smaller class sizes will also be needed.
(2) Class size reduction may have unintended consequences.
(3) Generalization requires careful adaptation. Every classroom has a unique and specific context.
One primary difficulty encountered by the SAGE project was the availability of funds for teachers but not space. Each district was then left to this potential problem in their own unique way. In schools constrained by space this often involved tag-team teaching rather than increased individualized instruction (lowering of PTR but not class size).
Results from the study demonstrated increased teacher satisfaction with job, increased communication with parents, and (as with Project STAR) long term increases in student graduation rates and admission into college. Although no significant differences were observed in the gains of both male and female students, improved outcomes were again larger amongst minority and disadvantaged students.
Lessons from Project SAGE
Teacher training was still not an integrated/funded component of the reform, thus it was noticed that in districts which lacked the space for more classrooms and thus employed team teaching, the tendency was to fall back onto a one teacher at a time model which only reduced PTR and not group size. Thus, Graue, the lead researcher noted that "although there was more space for them to do these things, the error was in assuming that teachers know how to navigate that space.” And noting the need for further systemic changes,"class-size to them became one cog toward greater student achievement, but if the whole machine did not change in conjunction, then the cog was inconsequential." 
Benefits in the UK
In a British study, students were closely observed by teams of researchers who recorded their “moment to moment” behaviors in blocks of 10-second intervals. The researchers found that adding five students to a class decreased the odds of students’ being on task by nearly a quarter. In classes of 30, low-attaining students were nearly twice as likely to be disengaged as they were in classes of 15.
Contrary to some class-size studies conducted in the United States, the British researchers found no “threshold effect” in their study. In other words, classes did not have to be reduced to 15 or 20 students before the behavioral benefits started to kick in. Reducing class size at any end of the class-size spectrum seemed to help.
L. A. Times teacher effectiveness study
A multivariable study commissioned by the Los Angeles Times looked at over 750,000 student-years worth of data from the L. A. Unified School District. The study reported that class size was unrelated to the teacher's effectiveness. Average class size in the study was 28 students.
The study looked at "value added", and therefore took into account the student's past performance. The dominant cause of value added to a student's performance was the teacher, although teachers showed a wide variation in how much value they added (or even subtracted). "For example, a typical student moves from the 50th ELA percentile with an average teacher to the 58th percentile for a teacher one standard deviation above the average. The gap in math is larger, where the student moves from the 50th math percentile with the average teacher to the 61st percentile for a teacher one standard deviation above the average."
Teachers with less than 3 years experience showed a small negative effect in their value added. Teachers with degrees beyond a Bachelor's or with "full teaching credentials" show no statistically significant difference in value added over teachers without these qualifications. Similarly, class size (for the ranges encountered) showed no statistically significant change in the value added to the students.
The validity of this study has been challenged by the National Education Policy Center in Colorado. Their evaluation of the Los Angeles Times'study concluded "The research on which the Los Angeles Times relied for its August 2010 teacher effectiveness reporting was demonstrably inadequate to support the published rankings. Using the same L.A. Unified School District data and the same methods as the Times, this study probes deeper and finds the earlier research to have serious weaknesses."
Subsequent research reviews
Subsequent research reviews have found that smaller classes beneﬁt all pupils because of individual attention from teachers, but low-attaining pupils beneﬁt more at the secondary school level. Pupils in large classes drift off task because of too much instruction from the teacher to the whole class instead of individual attention, and low-attaining students are most affected. Students beneﬁt in later grades from being in small classes during early grades. Longer periods in small classes resulted in more increases in achievement in later grades for all students. In reading and science, low achievers beneﬁt more from being in small classes. The beneﬁts of small class sizes reduce the student achievement gap in reading and science in later grades.
Difficulties of implementation in California
In California, implementation of class size reduction (and the increased need for classroom space and staff) has on the whole been seen as unsuccessful. Underfunded as a program, classroom space was taken from programs like special Ed and art as well as computer labs and libraries to meet the mandates of the reform. Schools serving the most low-income, English language learners, and students of color were thus often hit hardest, often forced to install portables at higher costs than reimbursed by the state (only $650/student in California when Wisconsin had invested $2000/student under SAGE). Additionally teaching staffs suddenly increased by 38%, which caused many to call into question the availability of sufficient quality teachers.
Supporters of class size reduction point out that, despite these criticisms and given that class sizes in California shrank from only 40 to 30 students per class (where the maximum was 24 under Project STAR and SAGE), "test scores did increase throughout the state and throughout all socio-economic levels--something no other reform has yet to accomplish." 
“Smaller classes provide opportunities for teachers to engage in practices that improve student achievement. Some teachers take advantage of these opportunities; other do not. When teachers take advantage of these opportunities, the likelihood of increasing student achievement is greater.” 
The need for teacher training to unlock the full potential of reduced class sizes was one of the main findings of Project SAGE.
“SAGE, in particular, and class size reduction in general, allows teachers the space to create meaningful learning opportunities for students. Giving teachers support to develop new strategies for teaching smaller groups makes it more likely. The presumption that change will naturally occur in teacher practice was not borne out in our observations and interviews. It would be a shame to reduce the power of this reform by not helping teachers and administrators to develop new practices matched to smaller groups. This is a step towards different kinds of teaching, one that requires guidance, reflection, and innovation.” 
Measuring the effects of reduced class sizes
Though Project Sage also incorporated assessment mechanisms beyond standardized tests (teacher interviews, day visits, collection of artifacts), both seminal studies focused primarily on demonstrating student improvement on standardized tests.
However, noting the increased longevity of student interest in education after attending smaller classrooms in their earliest years, some have wondered if CSR effects go beyond standardized test scores and, importantly, if these types of test truly even measure and encourage the best use by teachers of the potential value of smaller classes.
Others, primarily those who once repeatedly stated that there "are no benefits to reducing class size" and that "reduced class sizes should not be studied" disagree. According to Dr. Eric Hanushek “yes, whenever I say 'teacher quality,' it's synonymous with the rate of achievement scores of kids in classrooms.”  Thus, while all agree that teacher quality is important, political sides continue to be split on both how to determine the quality of a teacher and whether class size reduction helps or hinders efforts to best recruit, support, and utilize quality teachers.
Economics of smaller classrooms
Given the current uncertainty of national financial markets, some commentators have encouraged policymakers to consider whether implementing or broadening class-size-reduction policies is feasible in a time of major budget cuts.
In contrast, teacher magazine polls show that greater than 70% of current teachers cite lack of time for personal development, NCLB, and too large of classes as their primary barriers to both job satisfaction and their ability to teach. This has led proponents of class size reduction to note that low teacher retention rates lead to higher retraining costs and contribute to the current lack of qualified teachers. When faced with a constant flux of new teachers, student achievement has also been shown to suffer. Students who go on to finish their education also bring more value to their communities causing some economists to suggest that smaller class sizes may pay for themselves internally, although other economists question this. Some successes of the current charter school movement has been attributed to their generally smaller class sizes.
- Hattie, J. (2005, August), What is the nature of evidence that makes a difference to learning? Keynote address presented at the 2005 Research Conference, Lumina Grand Hyatt Hotel, Melbourne, 7–9 August 2005.
- Biddle, B. J. & Berliner, D. C. (2002) Research synthesis: small class size and its effects, Educational Leadership, 59(5), 12–23.
- Eric Hanushek (1999) “The Evidence on Class Size,” in Earning and learning: How schools matter, edited by Susan E. Mayer and Paul E. Peterson (Washington, DC: Brookings Institution): 131-168
- Graue, M. E., Hatch, K., Rao, K., & Oen, D. (2007). The wisdom of class size reduction. American Educational Research Journal, 44(3), 670-700.
- Blatchford, Peter; Bassett, Paul; Brown, Penelope (2011). "Examining the effect of class size on classroom engagement and teacher—pupil interaction: Differences in relation to pupil prior attainment and primary vs. secondary schools" (PDF). Learning and Instruction 21: 715–30. doi:10.1016/j.learninstruc.2011.04.001.
- Konstantopoulos, Spyros; Chung, Vicki (2009). "What Are the Long-Term Effects of Small Classes on the Achievement Gap? Evidence from the Lasting Beneﬁts Study" (PDF). American Journal of Education 116 (1): 125–54. doi:10.1086/605103.
- Achilles, C. M., Finn, J. D., & Bain, H. P. (1997). Using class size to reduce the equity gap. Educational Leadership, 55(4), 40-43.
- Molnar, A., & Zmrazek, J. (1994). Improving the Achievement of Wisconsin's Students. Urban Initiative Task Force Recommendations and Action Plan. Bulletin No. 95079. Wisconsin: Wisconsin State Dept. of Public Instruction, Madison. Bureau for Policy and Budget.
- Wang, M., & Finn, J. D. (2000). How Small Classes Help Teachers Do Their Best: Recommendations from a National Invitational Conference. CEIC Review, 9(2).
- Achilles, C. M., Finn, J. D., & Pate-Bain, H. (2002). Measuring class size: Let me count the ways. Educational Leadership, 59(5), 24-26.
- Zahorik, J., Halbach, A., Ehrle, K., & Molnar, A. (2003). Teaching practices for smaller classes, Educational Leadership, 61(1), 75-77.
- Achilles, C.M., Finn, J.D., & Bain, H.P. (1997). Using class size to reduce the equity gap. Educational Leadership, 55(4), 40-43.
- Elaine K McEwan, Patrick J McEwan: Making Sense of Research: What’s Good, What’s Not, and How to Tell the Difference, Corwin Press, 2003, p. 86
- Ehrenberg, R. G., Brewer, D. J., Gamoran, A., & Willms, J. D. (2001). Class size and student achievement. Psychological Science and the Public Interest, 2(1), 1-30.
- Bain, H.P. & Achilles, C.M. (1986). Interesting developments in class size. Phi Beta Kappan, 67,662-665.
- Mosteller, F. (1995). The Tennessee study of class size in the early school grades. The Future of Children, 5, 113-127.
- Stecher, B., Bohrnstedt, G., Kirst, M., McRobbie, J., & Williams, T. (2001). Class-size reduction in California: A story of hope, promise, and unintended consequences. Phi Delta Kappan, 82(9), 670-674.
- Graue, E., Hatch, K., Rao, K. & Oen, D. (2007). The wisdom of class-size reduction.American Educational Research Journal, 44(3), 670-700.
- , Buddin, Richard, "How Effective Are Los Angeles Elementary Teachers and Schools?"
- Graue, E., Hatch, K., Rao, K. & Oen, D. (2007). The wisdom of class-size reduction. American Educational Research Journal, 44(3), 670-700.
- Jepsen, C., and S. G. Rivkin (2002): “What Is the Trade-Off Between Smaller Classes and Teacher Quality?” National Bureau of Economic Research, Cambridge, MA.
- Anderson, L. W. (2002). Balancing breadth and depth of content coverage: Taking advantage of the opportunities provided by smaller classes. In J. D. Finn & M. C. Wang (Eds.), Taking small classes one step further (pp. 51-61). Greenwich, CT: Information Age Publishing.
- Cahen, L. S., Filby, N., McCutcheon, G., & Kyle, D. W. (1983). Class size and instruction: A field study. New York: Longman.
- Rice, J. K. (1999). The impact of class size on instructional strategies and the use of time in high school mathematics and science courses. Educational Evaluation and Policy Analysis, 21(2), 399-414.
- Slavin, R. (1989). Achievement effects of substantial reductions to class size. In R. Slavin (Ed.), School and classroom organization (pp. 247-257). Hillsdale, NJ: Earlbaum.
- Stasz, C., & Stecher, B. M. (2002). Before and after class size reduction. In J. D. Finn & M. C. Wang (Eds.), Taking small classes one step further (pp. 19-50). Greenwich, CT: Information Age Publishing.
- Blatchford, P. (2003). The class size debate: Is small better. Maidenhead: Open University Press.
- "Elements of High Quality Education - Dr. Eric Hanushek". Childrenofthecode.org. Retrieved 2012-01-01.
- "Quality Counts" (PDF). Retrieved 2012-01-01.
- "Teacher Magazine: Reader Polls". Edweek.org. 2008-09-10. Retrieved 2012-01-01.
- Krueger, A.B. (2003). ‘Economic considerations and class size’, Economic Journal, 113(F34–63).
- Class-Size Reduction Research from classsizematters.org
- Fact Sheets on Class Size from classsizematters.org
- "Identifying and Implementing Educational Practices Supported By Rigorous Evidence: A User-Friendly Guide" (2003) U.S. Department of Education, Institute of Education Sciences, National Center for Education Evaluation, and Regional Assistance, and the Coalition for Evidence-Based Policy