This book on classification abilities is part of a series designed to assist beginning and experienced teachers in becoming regular evaluators of their own instruction. The book consists of two sections. The first section provides information on: resemblance and consistent/exhaustive sorting; multiple membership and inclusive classifying; and horizontal and hierarchical reclassifying. The second and far longer section consists of 12 self-directed and self-instructive workshops. The goals of these workshops are to: (1) use a clinical method to administer, at any grade level, diagnostic tasks to ascertain classification abilities; (2) identify the developmental level of each student in terms of classification abilities; and (3) select, from resources available, subject matter (content and manipulative materials) appropriate to the identified levels of development in students' classification abilities. Except for the first workshop, the order in which workshops are completed or the number completed are at the discretion of the teacher. A short review of some research on classification abilities, a bibliography, and a sample record form are included. (JN)