I saw a chap of 20ish on the Tube today. He was wearing a King's College London top and pouring over a previous exam question sheet.
And that skill he was acquiring (and millions like him), to be able to absorb and briefly retain facts, is one that I have never, ever used in adult life. It is a life skill you simply do not need in almost every occupation - except possibly politics (which I think says more about that profession than the value of revision).
Effectively this means that one term in three is given over to learning a skill that is of no value to the individual or to society.
And it's sunny out, which is another reason why exams are loathsome.