You’re 15, in a maths lesson, and your class teacher announces that today you are going to learn about percentages.
You don’t understand percentages. You did for a week or two last year, and also the year before that. In fact, it is quite possible that you have understood percentages (for a week or two) every year since you were 10.
Maths in secondary school is taught in topics. Once you’ve learnt percentages, you will move onto equations, or probability, or some other topic that may even feel like a separate topic altogether. Maths has always been taught like this, so why the problem?
There are two problems: first, by the time you are 15, you don’t want to be learning percentages for the fifth time, knowing you’ll forget it in a couple of weeks; second, teaching in this way can often make maths seem like a series of discrete, rather than interconnecting range of topics.
Of course, the brightest students, to whom maths comes easily, will remember from year to year how to do each topic, will see links between topics for themselves, and will continue progressing towards an A or A*. But for the substantial majority of students whose only goal is a C, they forget what they have learnt pretty rapidly.
The solution is to give students the opportunity to review what they have learnt, as well as to learn the new stuff. I believe that for students aiming for a C at GCSE, over half of their classroom time should be devoted to reviewing what they already know (or, should I say, have been taught.) With maths, if you don’t use it, you soon lose it. As adults, with our secondary education well behind us, most of us are familiar with this.