The Comprehensive Tests of Basic Skills (CTBS) is a norm- and criterion-referenced achievement assessment for students in kindergarten through 12th grade, developed by CTB, a Macmillan/ McGraw-Hill Company. The fourth edition of the test was developed between the years 1984 and 1989. The Comprehensive Test of Basic Skills is made up of 11 testing levels that measure student achievement across the following subject areas: mathematics, study skills, science, and social studies. The CTBS is available in three configurations: the Benchmark Battery, the Survey Battery, and the Complete Battery.

The Benchmark Battery 190 Implementation and Performance in New American Schools and the Survey Battery are solely norm-referenced assessments (where Survey is a shortened version of Benchmark), whereas the Complete Battery also includes a criterion-referenced section. The Comprehensive Test of Basic Skills was nationally standardized separately for both spring and fall administrations in 1988 using a stratified random sample of 156,000 (spring) and 167,000 (fall) K–12 students drawn from public, Catholic private, and non-Catholic private schools. The test drew on a wide variety of curriculum and existing assessment instruments in order to identify broad concepts common to all curricula. This information was used to ensure that the entire test was not content specific and to formulate broadly applicable criterion for the criterion-referenced portion of the exam. A newer version of the Comprehensive Test of Basic Skills, known as Terra Nova, was normed in 1996. However, the CTBS assessment data referenced in this report are from the older version of this test, the Comprehensive Test of Basic Skills-4.