Sometimes schools get it wrong. It may even be that there are some schools led by nefarious headteachers who, in an effort to game league tables, seek to get rid of those students who are most likely to jeopardise their positions. It may even be the case that in a few case these students are more sinned against than sinning. But this is, I think most people would agree, a relatively rare scenario. It’s actually fairly difficult to exclude students:…