Teaching and learning happen in time and over time. The blocks of teaching in a school day are punctuated by breaks. A topic that begins as a trickle on a Monday can have matured by Friday. The seasons and school holidays provide stepping stones around which teaching flows. Material is organised in timetable slots and units of work. A class of children work and grow with one another and with the teacher over the course of a year. Anything worth learning takes time. But how long? The time needed may vary from teacher to teacher and from child to child.