Development of The Assessment of Basic Competencies (ABC), a test battery based on the three-parameter logistic model, is described. Eleven dimensions of intellectual growth are measured, from the pre-kindergarten level through ninth grade. An educationally relevant skill domain is represented by each test. Unique properties of the test, based on item characteristic curve theory, are reviewed and two procedures utilized in developing the battery are described. The methods used to place each test's items on a common metric and to generate scoring tables for each test are described. Overlapping subtests or overlapping groups of testees are not required, and hand-calculated test scores can be converted into a maximum likelihood point estimate and a distribution-free interval estimate of the testee's ability. (Author/MH)