The term ‘curriculum’ means different things to different people. For administrators, including headteachers, it often refers to the organisation of school subjects and the allocation of times when each subject is taught, as depicted upon the school timetable. For class teachers, the term embraces the content of what should be taught during each of these timetabled periods, that is a scheme of study presented in the form of a syllabus. However, even simple interpretations such as the above beg a number of questions which immediately lead us to expand our definition of the curriculum. Looking at the timetable, for example, we might observe that mathematics is allocated twice the amount of time allocated to geography and nearly four times that given to art or PE. This leads us to ask what rationale governs these decisions. Is mathematics deemed more important or are its concepts more difficult to master and therefore require a greater number of periods on the timetable? When we examine the content of what is taught in each of these subjects, more questions emerge. Why this topic rather than that one? Why do we teach x in a subject before we teach y? Decisions concerning the sequence of topics may in part be a question of logic but in some cases such decisions are influenced also by what we know about principles of learning which suggest that some topics are too difficult for pupils of a certain age or ability.