John B. Carroll's Model of School Learning is a paradigm which describes the degree of learning that takes place in school setting as a function of the time spent on a learning task divided by the time needed for its mastery. The components of opportunity and perseverance in Carroll's model have particular relevance to a form of school organization such as nongradedness which has as its primary objective the provision of unlimited time opportunity during which a student can actively engage in a learning task until the time spent is commensurate with the time needed. The purpose of this study is twofold: 1) to identify Carroll's model as a possible theoretical basis for the organizational structuring of schools and 2) to test seven hypotheses derived from the model which concern the amount of perseverance and the degree of learning that actually occur under varying conditions of quality of instruction and ability to understand instruction when unlimited time opportunity is available. The sample consists of 160 students divided into three ability levels, randomly assigned to two levels of treatment. Statistical analysis are made by way of ANOVA, ANCOVA, and Fisher's transformation to z. (Author)