I know it seems a long way off when you're fighting the battles to get your children into a "good" senior school (grammar or otherwise), but my eyes have been opened recently to the problems that going to a good school may cause when applying to university.
Friends of ours are anxiously waiting for university offers and to my horror, I keep hearing stories of pupils with pretty much all A* at gcse and 3 or more As at AS level being rejected for places on their chosen course.
Inevitably, with grade inflation and so may applicants achieving the highest grades, there are not going to be places for everyone. However, of greater concern to me is that more and more universities are looking at the average gcse and A level scores achieved at the applicant's school. If the applicant achieves below that average, then he/she will lose points on their application and is likely to be rejected. The end result may be that your dc achieves easily high enough grades for the particular course they apply for, but because they "only" achieved 6 A* and the average at their school was 8, they will be penalised!
I know attending a good school is so much more than just the grades you achieve at the end (friendships, other opportunities etc) but I'm starting to wonder whether sending them to a good school is just saving up the problems for the future, particularly if they just happen to be not at the top of the school!