In NSW, the UAI was determined by a combination of the public HSC exams common across all schools at the end of Year 12 and continuing assessment.
The UAI attempted to rank students who did not progress to their senior years of High School, by estimating what they would have got.
The student who came first in the subject was then assigned the maximum mark, normally 50.0 on a one unit basis but may have changed with scaling.
This was because the spread of marks took into account those who did not complete their HSC or otherwise attend the post-compulsory years of education.
As their marks were generally lower than those who complete the HSC, they caused the uneven spread across the spectrum of the UAI.
Students who finished high school overseas and who had a qualification such as the SAT, International Baccalaureate or A Levels may have had their score converted to a UAI.
Also, a number of international schools had adopted the ACT curriculum and assessment regime such that their studies culminated in the award of an ACT-calculated UAI.
During June 2009, the Federal Minister for Education announced the removal of UAI and the introduction of the Australian Tertiary Admission Rank, or ATAR, for Year 12 students of 2009 within the ACT and New South Wales, and for the rest of the country excluding Queensland in 2010.