Sorry to use the term 'spoon feeding', I know it is a bit emotive.
Teaching students who have been to the 'best' schools - both state and private- , it is often hard to avoid the impression that they have been 'coached' and given a very clear idea of what to write for particular exam questions (e.g. a list of bullet points). They have also obviously been given intensive help with their coursework. This is not a criticism of the schools or the teachers, clearly this is the best way to get the best results at A-Level.
(This raises a whole other set of questions about what A-Level tests, but that is another thread.)
However, it does not necessarily prepare the students that well for some degree courses, where they have to work extremely independently, and write a very different sort of essay. In some cases, the very bright student who has been to a more ordinary school, and has had to work on his/her own more, will cope better.
E.g. what margotfonteyn says about teachers reading 'first drafts' - yes, this can help students with their essay writing, but when they get to university and no longer have someone to read their first draft, it can be rather disorientating and disconcerting.