Aptitude tests have as their purpose the measurement of aptitude, or potential. These tests are different from, but similar to intelligence quotient (IQ) tests. These tests are considered predictive in nature, forecasting how the tested individual can be expected to perform in the future. Many schools administer some form of aptitude test beginning in early grades. Some post-secondary school curricula programs also use aptitude testing as part of pre-enrollment criteria.
In general, aptitude tests have a progression as students move from lower grades up to the post-secondary school level. Aptitude tests for lower grades are generalized, predicting overall performance over a range of learning areas. As the student advances through grade levels, the aptitude testing that she might encounter tends to become more specialized, focusing on particular subject areas or particular skills supportive of learning certain disciplines, such as mathematics or writing. Aptitude tests administered as part of the enrollment criteria for post-secondary school curricula focus specifically on the skills needed to learn successfully the particular discipline the program is designed to teach. For example, a technical writing curriculum aptitude test obviously tests aptitude related to writing skills; such a test, however, also may involve aptitudes related to understanding programming or Hypertext Markup Language (HTML).
In contrast to aptitude testing, achievement tests test an individual on the level of skill in a discipline or subject the student has studied in some form. This type test measures the actual level of previously acquired knowledge. Achievement tests are generally more subject-specific than aptitude tests, testing a single knowledge base area. While a variety of achievement tests exist, educators most commonly use a handful of such standardized tests.
The six most common standardized achievement tests are: the Iowa Test of Basic Skills (ITBS), the Stanford Achievement Test (SAT, which is different from the Scholastic Aptitude Test, also known as SAT), the California Achievement Test (CAT), the California Achievement Test, Fifth Edition (CAT/5), the Comprehensive Test of Basic Skills (CTBS) and the Personalized Achievement Summary System (PASS).
The Iowa Test of Basic Skills allows testing of a wider grade range of students at the same time, takes less time to administer than the Stanford test and is considered to be among the most difficult of the standardized tests. The Stanford test is a top-rated test that covers kindergarten through grade 12. The California Achievement Test, because it encompasses more traditional values that other standardized tests, enjoys popularity among Christian schools and home schools. The Comprehensive Test of Basic Skills tests comes with a professional critique and tests all academic areas inclusive of language arts, reading, spelling, science, math, social studies and reference skills; it covers grades 1 through 12. The CAT/5 is an updated version of the Comprehensive Achievement Test, covering a wider grade range. Finally, the Personalized Achievement Summary System is designed specifically to test achievement among home-schooled students.