The purpose of this study is to contribute to research regarding the Application of Cognitive Functions Scale (ACFS; C. Lidz and R. Jepsen, 1997), a newly developed dynamic assessment approach for the assessment of preschool children. The ACFS assesses the ability of children to apply their cognitive functions in areas that are related to the development of foundations for successful school achievement. This study examined the theory of dynamic assessment and reviewed the literature on dynamic assessment and school psychology. The study also examined the validity of three subtests within the ACFS procedure. Participants were 20 preschool children between the ages of 3 and 4 years. Results show significant pre- to posttest gains (with some exceptions noted) that suggest that practice effects alone do not account for the gains on the subtests. (Contains 3 tables and 20 references.) (Author/SLD)