Well on Radio 4 according to one turned around teenager this morning it was the fault of teachers who didn't give one to one teaching in secondary school.
However he got the one to one when he went onto college.
Of course no mention of the time constraints on secondary teachers who will be teaching at least 21 classes out of 25 in a week on average and then rely on teaching extra sessions at the end of the day to help smaller groups of examination students to help catch-up.
Of course many lecturers at college have 2-3 classes in lower and upper years and therefore do have time to give to supporting poorer performing students..