Australian Tertiary Admission Rank
The Australian Tertiary Admission Rank (ATAR) is the primary criterion for entry into most undergraduate-entry university programs in Australia. It was gradually introduced during 2009 and 2010 to replace the Universities Admission Index, Equivalent National Tertiary Entrance Rank and Tertiary Entrance Rank. Queensland still retains its own separate Overall Position system, but will begin using the national ATAR system for year 10 subjects in 2018, and for year 12 students graduating in 2020.
Where is their English scaled study score, is the sum of their three best scaled study scores excluding English, and is the sum of their next best two study scores. Because ATAR is ranked on averages, a new table is published each year for mapping aggregate scores to ATAR (e.g. 159.8 aggregate = 90.00 ATAR in 2013).
Other states vary, e.g. in Queensland, English needs to be passed but will not be a mandatory component of the ATAR.
Overview in some states
The ATAR is a percentile score given between "less than 30" up to 99.95 (in a minimum increment of 0.05) which denotes a student's ranking relative to their peers upon completion of their secondary education. For example, an ATAR score of 99.0 means that the student performed better than 99% of their peers, and ranks lower than 0.95% of peers (as the maximum score is 99.95). "Peers" is not the body of students receiving an ATAR that year, but a notional body of persons who might be qualified to receive an ATAR – as a result, the median ATAR score is well above 50.00. For example, the median ATAR score for 2014 was 68.95.
This score is used by university and tertiary education programs as a clear and intuitive ranking to select prospective applicants for their programs, though other means may be used in combination (such as the UMAT for undergraduate-entry medical studies, or interviewing candidates that meet an ATAR score threshold).
The ATAR score is derived from a single aggregate score that is the sum of the four highest scoring subjects that the student has completed at a year 12 standard added with 10% of the sum of the weakest two subjects if the student has elected to study further subjects. The maximum number of subjects used in the calculation of the aggregate score cannot surpass six (four subjects contributing their full amount, and the last two contributing 10% of their respective score), therefore additional subjects completed in excess will re-order the scores used in the determination of the ATAR such that the lowest scores beyond the six will be ignored entirely. Certain subjects (such as university-level courses for high achievers) may also have restrictions such that they may only be used as one the lowest two contributing scores, or mandated to be one of the top four contributing scores (such as compulsory English subjects).
Each completed year 12 subject mark that contributes to the ATAR calculation is referred to as a 'study score', which is a normalized score between 0 and 50 for a study undertaken at a year 12 level (with integer increments). This is similar to the percentile ranking featured in the ATAR score itself.
Given the discrepancy of difficulty and competition between the wide ranges of subjects offered as part of secondary school education in Australia, these subjects are normalized against each other by means of some sort of study score scaling. For example a score of 89 in Psychology might be scaled to 77, while a score of 89 in Physics might be scaled to 84.  Details of this scaling are not (easily) available. Individual universities might also have their own scaling systems. Scaled marks are not reported to students.
Another example is that being at the 99% percentile for Standard English can only produce a scaled mark of 40 (out of 50) while that same scaled mark can be achieved by being at the 70th percentile for English Extension. 
The ATAR follows the same principles as its predecessors. The rank gives an indication to the overall position of the student in relation to the student body for that year across the state. A higher ATAR gives preference to that student for the course to which they wish to enrol in a university of their choice. The ATAR is used by: the Universities Admissions Centre (UAC) in New South Wales and the Australian Capital Territory; the South Australian Tertiary Admissions Centre (SATAC) in South Australia and the Northern Territory; Victorian Tertiary Admissions Centre (VTAC) in Victoria; and Tertiary Institutions Service Centre (TISC) in Western Australia. Starting in 2020, when the year 12 students graduate, the Queensland Tertiary Admissions Centre (QTAC) in Queensland will also use and calculate the ATAR. These bodies then allocate positions for the tertiary institutions in their relevant states.
Is the best 5 subjects. English needs to be passed, but not necessarily included in the total. There is some sort of inter-subject scaling. Tertiary institutions may also offer various bonuses.
Introduction of ATAR
During June 2009, the Federal Minister for Education Julia Gillard announced the removal of Universities Admission Index (UAI) and the introduction of the Australian Tertiary Admission Rank, or ATAR, for Year 12 students of 2009 within the Australian Capital Territory and New South Wales, and for the rest of the country, excluding Queensland, in 2010. The ATAR was introduced to unify the university entrance system in Australia, where previously each state or territory had its own individual system (UAI in ACT/NSW, TER in SA/NT/WA/TAS, ENTER in Victoria). Now in Queensland, the OP system is planned to change to the ATAR system from 2019.
2016 ATAR error
In 2016, a computer error allowed for 2075 students to receive their ATAR score five days earlier than they were supposed to be announced. External SMS provider for VCAA, Salmat Digital, created an error that allowed for students to receive their results by texting VCAA and requesting their scores to be sent to them on the expected release date. This sparked outrage from parents of students who did not receive their scores, citing that they considered it "unfair", as well as concern about some students receiving their results before they were equipped to deal with them (particularly with regards to counselling).
Changes from UAI
The shift to ATAR means that the ranks most students receiving a UAI would increase by a small amount (although this would not present as any advantage as cutoffs would subsequently increase), while the maximum rank in NSW/ACT would change from a UAI of 100 to an ATAR of 99.95. Queensland will not shift to the ATAR system because it uses a different system and ranking scale, the Overall Position; however, conversion tables to or from the ATAR are available.
- "ATAR 2020 - QTAC". www.qtac.edu.au. Retrieved 2017-08-12.
- "OP score to go in Queensland in 2018; replaced by Australian Tertiary Admission Rank system". 25 August 2015. Retrieved 20 May 2016.
- "How is ATAR Calculated? - MathsMethods.com.au". MathsMethods.com.au. 21 August 2014. Retrieved 2 February 2017.
- "New tertiary entrance rank". 18 January 2017. Retrieved 17 February 2018.
- According to the Universities Admissions Centre which administers ATAR-based tertiary entry for NSW and the ACT. "Archived copy" (PDF). Archived from the original (PDF) on 1 March 2015. Retrieved 2015-03-03.
- "Victoria: How the ATAR is calculated". 13 December 2010. Retrieved 20 May 2016.
- "NSW: ATAR calculation". Retrieved 20 May 2016.
- "UAC ATAR".
- "Matrix All about scaling".
- "This is my year - QTAC". www.qtac.edu.au. Retrieved 2017-08-12.
- "ATAR 2020".
- "ACT adopts national student ranking system". ABC News (Australian Broadcasting Corporation). 10 June 2009. Retrieved 16 December 2010.
- Rania Spooner, Henrietta Cook, Bianca Hall and Timna Jacks (8 December 2016). "Fear and worry as VCE results are issued days early". The Age. Retrieved 26 December 2016.
- Australian Tertiary Admission Rank (ATAR) - UAC Archived 12 November 2009 at the Wayback Machine.
- "2012 Australian Year 12 Conversion Table". Queensland Tertiary Admissions Centre (QTAC). 2012. Archived from the original on 4 May 2013. Retrieved 16 May 2013. Note: This site gives the 2012 conversion table, which is approximate. The 2013 conversion table is likely to be slightly different.