Piaget's model of children's conceptual learning and development was compared with Klausmeier's Conceptual Learning and Development (CLD) model in a longitudinal study. The CLD model suggests four successive levels of concept learning: (1) concrete--recognizing an object which has been encountered previously; (2) identity--recognizing a known object when it appears in a different spatial, time, or sensory perspective; (3) classificatory--generalizing that two items are alike in some way; and (4) formal--naming and defining the concept, listing its attributes, and judging the presence of such attributes in an object. The CLD assessment batteries, designed to assess the attainment level and use of three concepts (equilateral triangle, noun, and tree), Piagetian logical concept tasks assessing classificatory, relational, numerical, and conservation abilities; and three memory measures were administered to 180 kindergarten, third, and sixth grade children. One year later, 156 of these subjects were tested again; data on these subjects are summarized for the first two years of study. Results of pass/fail contingency analyses relating performances on the various measures are given, as well as results of correlational and factor analyses. (Author/GDC)