I have to agree with you there, Stevo. A girl I know is amazing at all of her subjects, and she spends all of her time working. She's very nice, but is rather lacking socially. There have been many times when I've wished that I was as good at maths and the sciences as her, but is it really worth it?
Then again, she'll probably end up in Oxbridge and yes, then it will be worth it! Lol.
Oh, and concerning the whole State School/Private School thing, I went to a state school and am going to a state Sixth Form, and our school is generally known for shortness of skirts, lack of facilities and high teenage pregnancy rate and smoking. Despite that, all of my close friends as well as several other people I know did do very well at GCSE's, and they will probably continue this on to A-level.
At the end of the day, although bad teaching and facilities can have a negative difference, if you're ready to work for it, you'll still be able to achieve to the best of your abilities no matter where you go. Alternatively, if you go to a private school, that doesn't automatically mean that you're going to do well. It's all up to the individual.