In this paper we seek to provide an explanation of three widely documented empirical phenomena. These are: (i) increasing educational participation rates; (ii) little change in class differentials in these rates; and (iii) a recent and very rapid erosion of gender differentials in educational attainment levels. We develop a formal mathematical model, using a rational action approach and drawing on earlier work that seeks to explain these three trends as the product of individual decisions made in the light of the resources available to, and the constraints facing, individual pupils and their families. The model represents children and their families as acting rationally, i.e. as choosing among the different educational options available to them on the basis of evaluations of their costs and benefits and of the perceived probabilities of more or less successful outcomes. It then accounts for stability, or change, in the educational differentials that ensue by reference to a quite limited range of situational features. So, both class and gender differences in patterns of educational decisions are explained as the consequence of differences in resources and constraints. We do not, therefore, invoke `cultural' or `normative' differences between classes or genders to account for why they differ in their typical educational decisions (though we have something to say about the role of norms in such an account). Because the model is presented mathematically, testable corollaries are easy to derive as are other implications of our model for patterns of relevant behaviour.