Dual language is a form of education in which students are taught literacy and content in two languages. The majority of dual language programs in the United States teach in English and Spanish, although increasing numbers of programs use a partner language other than Spanish, such as Arabic, Chinese, French, Hawaiian, Japanese, or Korean. Dual language programs use the partner language for at least half of the instructional day in the elementary years.
Dual language programs generally start in kindergarten or first grade and extend for at least five years, although many continue into middle school and high school. There is one higher education (baccalaureate and masters) program in Florida. These programs aim for bilingualism (the ability to speak fluently in two languages), biliteracy (the ability to read and write in two languages), academic achievement equal to that of students in non-dual language programs, and cross-cultural competence. Most dual language programs are located in neighborhood public schools, although many are charter, magnet, or private schools.
Historical Context of Two-Way Immersion 
The initiation of dual immersion programs in the United States is characterized by the coalescence of local politicians and community members. Coral Way Elementary, an K-8 school in Dade County, Florida, is cited as the first two-way bilingual school, beginning in 1963 . The program was started by Cuban citizens who were seeking refuge in Florida from the Castro regime and believed that their children would eventually return to Cuban schools . The Ecole Bilingue, a French/English school in Massachusetts, was formed around the same time . In 1968, the passing of the Bilingual Education Act served to address the reality that Limited English Proficient(LEP) students were in need of proper instructional support to achieve academic gains, and in turn provided federal funding for primary language instruction in local school districts . The Lau v. Nichols ruling of 1974 further affirmed a student’s right to educational opportunity via appropriate instructional services (Calderón, 2000). Schools were thus charged with the mission to implement programs suitable to the needs of their language minority students.
While the number of dual immersion programs remained relatively low throughout the mid-1980s, a greater attention to the need to provide challenging yet comprehensible (Calderón, 2000) instruction to English language learners (ELLs), in more recent years, triggered a substantial growth in the number of programs. In 2002, for example, the implementation of the English Language Acquisition, Language Enhancement, and Academic Achievement Act of the No Child Left Behind Act subsequently made it requisite that schools with large numbers of language minority students provide instruction that facilitates their acquisition of English, to consequently perform well on standardized tests . There are presently three hundred and ninety-eight two-way immersion programs in thirty distinct states and the District of Columbia . The quantity of programs has increased significantly in the last decade, despite efforts made in states such as Arizona and California to eradicate bilingual education programs in favor of English-immersion, with the passing of Proposition 203 and Proposition 227, respectively. It is estimated ninety-four percent of the dual immersion programs are Spanish/English, with the remaining six percent either Chinese/English, Navajo/English, Japanese/English, and Korean/English programs (Bae, 2007).
Changes in the TWI Model Since its First Implementation 
One of the most salient changes that has occurred in the two-way immersion program since its inception is its conversion from a program centered predominately on aiding ELLs to develop fluency in English to an enrichment program striving for biliteracy, bilingualism and biculturalism for all students participating. Although two-way immersion was initially focused on supporting ELLs in their development and acquisition of English literacy skills, the need to develop bilingualism in an increasingly globalized society has made the program appealing for many parents of children who are native speakers of English (Calderón, 2000). Whereas foreign-language education programs can provide native speakers of English with exposure to a second language, TWI has the potential to help students achieve near fluency in a second language. This suggests that such programs are not solely focused on helping ELLs to acquire English, but instead aim to develop second language proficiency for native speakers of English. In fact, because two-way immersion requires almost an equal amount of native English and native Spanish speakers, if the former is lacking, it is likely that such programs will not be implemented, which implies that the latter may not receive the opportunity to take part in the dual immersion program (Gomez, 2005).
Types of Dual Language Program 
There are four main types of dual language programs, which mainly differ in the population:
- Developmental, or maintenance, bilingual programs. These enroll primarily students who are native speakers of the partner language.
- Two-way (bilingual) immersion programs. These enroll a balance of native English speakers and native speakers of the partner language.
- Foreign language immersion, language immersion or one-way immersion. These enroll primarily native English speakers.
- Heritage language programs. These mainly enroll students who are dominant in English but whose parents, grandparents, or other ancestors spoke the partner language.
The term "dual language" is often used interchangeably with two-way immersion. Other variations on dual language include "dual language immersion," "dual immersion," and "dual enrollment". The term bilingual education has somewhat fallen out of favor among dual language practitioners, but it is still used to refer to any program that uses two languages for instruction.
Dual language programs are different from transitional bilingual programs, where the aim is to transition students out of their native language and, in the United States, into English as quickly as possibly, usually in three years. This is sometimes referred to as subtractive bilingualism since the first language is typically lost as English is acquired. Dual language programs are considered to promote "additive bilingualism", meaning that students' primary language is developed and maintained as a second language is added.
Another type of program that is not considered dual language is foreign language education where students receive less than half a day studying in the partner language, and often only study language arts and literature in that language as opposed to content area subjects such as mathematics, science, and social studies.
Variation within Dual Language Programs 
There are two main variations: 1. Amount of time spent in the partner language 2. Division of languages
1. Time Spent in Partner Language
- Full immersion, or 90/10, programs teach in the partner language 90% of the time in the primary grades (usually kindergarten and first grade) and 10% in English, and gradually adjust the ratio each year until the partner language is used 50% and English is used 50% by third or fourth grade (sometimes later if the program extends through eighth grade or beyond).
- Partial immersion, or 50/50, programs teach 50% of the day in English and 50% of the day in the partner language at all grade levels.
There is currently no research indicating that one of these methods is preferable to another, although some research indicates that students who spend more time in the partner language do better in that language (Howard, Christian, & Genesee, 2003; Lindholm-Leary, 2001; Lindholm-Leary & Howard, in press), and that language minority students (in the U.S., those whose native language is not English) do better academically when their native language is supported and developed (Thomas & Collier, 1997; 2002).
Full immersion (90/10) programs typically begin literacy instruction for students in kindergarten and first grade in the partner language and add formal literacy in English in second or third grade. Students do not need to relearn how to read in English; teachers help them transfer their literacy skills from one language to the other. Other 90/10 programs separate students by native language and provide initial literacy instruction in the native language, adding second language literacy by second or third grade. In partial immersion or 50/50 programs, initial literacy instruction is either provided simultaneously in both languages to all students, or students are separated by native language in order to receive initial literacy in his or her native language.
Dual language programs in middle school and high school often merge students from several dual language elementary schools and exist as programs within larger mainstream schools. They often offer dual language students the opportunity to take language arts and at least one content area in the partner language, and many prepare students to take the Advanced Placement exams.
2. Division of Languages
- Language division by schedule: Within any dual language program, students speak and study in one language at a time, and the times for each language are explicitly defined. There is great variation, however, in the specifics. In some programs, language alternates by day, by week, or by several week periods. In other schools, students speak one language in the morning and the other language after lunch. After a designated amount of time, one, two, or more weeks, the morning and afternoon languages switch. Further variation includes programs where particular subjects are always taught in one language, due to resource availability. Within a given school or program, there may be different schedules for different grades, such as at the Amistad Dual Language School in New York City, where students alternate languages less frequently as they progress through the grades and establish stronger skills in both languages.
- Language division by instructor: A dual language program may use a Self-Contained or Side-by-Side model. Self-Contained programs have one teacher for one group of students in one classroom. The teacher transitions from one language to the other along with her or his students. Alternatively, Side-by-Side programs have two or more classrooms for each grade, where one teacher teaches in the partner, or target, language and the other teacher teaches in the dominant language (English in the United States). The grade is divided into two groups of students and the groups trade classrooms and teachers according to an explicit schedule, whether daily or weekly. Finally, at some schools, two or more teachers may team teach in the same classroom, with each teacher using one language and a combination of whole group, small group, and independent activities facilitated by the teachers.
Instruction in Dual Language Programs 
Dual language programs vary in the kinds of instruction they provide, but generally implement many of the following features:
- language arts instruction in both program languages
- instruction on literacy skills like phonics and fluency along with opportunities to read literature in both languages
- sheltered instruction strategies in both languages
- ability grouping for targeted purposes, with frequent reassessment based on strengths and weaknesses on different skills
- separation of languages, where the teacher will only speak one language at a time without translating, while allowing students to use native language resources such as peers and bilingual dictionaries
- ample time for student interaction (such as through the use of cooperative learning), allowing students to practice their new language skills with their peers
Dual language teachers also incorporate practices that should be in place in any classroom that includes linguistically diverse students:
- Teaching content so that it interests and challenges bilingual students
- Communicating high expectations, respect, and interest in each of their students
- Understanding the roles of language, race, culture, and gender in schooling
- Engaging parents and community in the education of their children
- Becoming knowledgeable about and developing strategies to educate bilingual students and to communicate with their families
- Seeking and obtaining the professional development needed to engender these attitudes, knowledge bases and specific instructional skills (Garcia, 2005).
In regard to lesson planning, dual language teachers should focus on creating lessons that:
- proceed from whole to part
- are learner centered
- have meaning and purpose for students and connection to their present lives
- engage groups of students in social interaction
- develop both oral and written language
- show faith in the learner in order to expand students’ potential (Freeman & Freeman, 1994)
Other important tips for educators teaching bilingual or multilingual students include organizing content around themes, providing students with choice, starting the learning process with students’ questions, and exposing students to not only professional published books and magazines but student-authored literature (Freeman & Freeman, 1994).
American programs 
- Key Elementary School in Arlington, VA
- Shuang Wen School in New York City
- Shuang Wen Academy Network in New York City
- Amistad Dual Language School in New York City
- High School for Dual Language & Asian Studies in New York City
- Escuela de Guadalupe in Denver, CO
- The International School in Portland, OR
- Coral Way Bilingual K-8 Center in Miami, FL
- Inter-American Magnet School in Chicago, IL
- Otay Ranch High School in Chula Vista, CA
- Rancho Del Rey Middle School in Chula Vista, CA
- Chula Vista Learning Community Charter (CVLCC)
For names of more dual language programs not profiled in Wikipedia, see The Directory of Two-Way Bilingual Programs in the U.S. or The Directory of Foreign Language Immersion Programs in U.S. Schools
See also - others 
Effectiveness of Two-Way Immersion 
Two-way immersion has been referred to as the most effective bilingual program contributing to long-term academic success (Howard et al. 2003, p. 24). Thorough planning and effective implementation are crucial to the success of TWI programs, in addition to ample support from administrators and access to quality resources. In well-implemented programs, ELLs have achieved higher academic success than their peers in other bilingual programs (Dorner, 2011). Effective implementation, for one, lies in the duration of the program. In order to produce academic achievement, students ideally must be enrolled in TWI programs for four to seven years (Howard et al. 2003, p. 24). Students participating in TWI programs for this length of time have been shown to demonstrate higher academic performance than their peers in English-immersion programs (Howard et al. 2003, p. 24). On the contrary, students who receive little to no instruction in their native language, during their elementary years, struggle to attain grade level performance in the target language (Cobb, 2006).
Both Native English Speakers (NES) and ELLs are beneficiaries of the gains made through TWI. The juxtaposed use of the majority and minority language in TWI programs can enable children to transfer skills from the secondary language to their primary language and viceversa (Scanlan, 2009). Research comparing the academic achievement made by native speakers of English and native speakers of Spanish illustrates that while both groups show growth in their native and secondary language, English native speakers are more dominant in their primary language, whereas Spanish native speakers are able to achieve a more balanced form of bilingualism, that is, relatively equal in their ability to communicate orally and in writing in their primary and secondary language (Howard et al. 2003, p. 36).
The evidence of the effectiveness of TWI is consistent in programs where less common languages are maintained as well. For example, an eight year study of the Navajo/English two-way bilingual program at the Rough Rock Community School in northeastern Arizona confirms that those students who received thorough instruction in their native language as well as the target language encountered more success in school than their peers in English-only programs (McCarty, 2000). Such students too showed progress in both languages in their writing abilities on local and national measures (McCarty, 2000).
In addition to quantitative measures of effectiveness, research has further credited the two-way immersion model as creating more unified communities in public schools amongst parents and caregivers, since speakers of both majority and minority languages are grouped together in an effort to develop literacy skills in both languages and consequently foster cross-cultural relationships in both cultures (Scanlan, 2009). Furthermore, studies have shown that high school students who attended schools with two-way bilingual programs were more motivated and passionate about attaining higher level education (Cobb, 2006).
While such examples attest to the effectiveness of the TWI model, these programs are often voluntary which signifies the inherent difficulty in making comparisons across programs. Academic success and biculturalism may be attributed to the quality of the TWI program, however may also be ascribed to external factors such as a student’s inherent qualities or socioeconomic status (Howard et al. 2003, p. 12). Thus, while standardized test scores, from a policy perspective, are often used to determine the effectiveness of a program, other elements may impact the academic success achieved by many students in the TWI program (Howard et al. 2003, p. 23).
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