This paper is part of a series of studies about the nature of expertise in teaching and the cognitions of effective teachers. A summary offered of psychological research on the nature of expertise indicates that experts often know more, in a more elaborate way, about the subject than novices and organize knowledge in a different fashion. It is also noted that tasks presented elicit different levels of schema--that is, the same elements in a task may be identified by both experts and novices, but key elements trigger deeper, and more elaborate schema for experts than for novices. A description is given of an evaluation study in which novices (observers with two years of classroom experience) and experts (teachers) estimated the overlap between the curriculum to which a child had been exposed and a criterion test for each child. Four of the teachers and three of the observers were further asked to provide a discussion of their thoughts while doing the overlap task. The quantitative findings are reviewed, and the qualitative findings are discussed in detail. Also included are quotations of subjects' thoughts, as the subjects formed conclusions on and predicted the potential abilities and expected achievement of the children. Directions for the overlap test are appended as well as diagrams illustrating the subjects' thought processes. (JD)