This paper applies a theory of growth in academic achievement to the study of the effects of ability grouping on reading achievement. The theory sees students' ability and effort determining how they utilize opportunities for learning provided by instruction. (Author/JAZ)

The purpose of this paper is to propose a conception of the learning process and to suggest its mathematical form. In this framework, the characteristics of the schools children attend are emphasized. The objective is to suggest a framework for the evaluation of research on school effects and a point of departure for new research on the impact of…