The Selective Schools Test is designed by the Australian Council for Educational Research, which has a long background in scholastic aptitude testing. Questions are written by special teams and then tested on small samples in other states.

The tests are developed to be to be unrelated to the syllabus. They are designed to assess higher level reasoning. This allows ability and aptitude rather than achievement to be measured. The main emphasis is on thinking and operating with words, numbers and ideas, as these are considered to be predictors of high school achievement.