How is the ATAR determined?
The NSW Board of Studies provides you with a profile of marks that indicate how you have performed in your courses in relation to course performance standards. Both the Board's marks and ATARs are derived from raw examination marks and moderated school assessments.
With the exception of English, which is compulsory, you are free to choose your courses of study. Consequently, individual course candidatures vary in size and nature, and there are many different enrolment patterns. Normally there are approximately 27,000 different enrolment patterns for ATAR-eligible students; approximately 20,000 patterns are taken by only one student.
Given the choice available, your rank in different courses will not necessarily have the same meaning, as a good rank is more difficult to obtain when you are competing against students of high academic ability. Because of the lack of comparability, your raw marks are scaled before they are added to give the aggregates from which ATARs are determined.
The scaling process is designed to encourage you to take courses for which you are best suited and which best prepare you for your future studies. The underlying principle is that you should neither be advantaged nor disadvantaged by choosing one HSC course over another. The scaling algorithm estimates what your marks would have been if all courses had been studied by all students.
Scaling modifies the mean, the standard deviation and the maximum mark in each course. Adjustments are then made to the marks of individual students to produce scaled marks. Although scaled marks are generally different from the raw marks from which they are derived, the ranking of students within a course is not changed.
Once the raw marks have been scaled, aggregates are calculated for ATAR-eligible students. In most cases, the order of merit based on these aggregates is quite different from the order of merit using aggregates based on HSC marks.
Percentiles, which indicate the ranking of students with respect to other ATAR-eligible students, are then determined on the basis of the aggregate of scaled marks.
The penultimate step is to determine what the percentiles would have been if all students in their Year 7 cohort completed Year 12 and were eligible for an ATAR. The last step is to truncate these percentiles at intervals of 0.05, commencing at 99.95. These are the ATARs.
Each ATAR corresponds to a range of aggregates.
The scaling process, which does not assume that one course is intrinsically more difficult than another or that the quality of the course candidature is always the same, is carried out afresh each year. All students who complete at least one ATAR course in a given year are included in the scaling process for that year.
Further information about the HSC can be found on the NSW Board of Studies website.
