My DS went through school doing reasonably well but as a quiet child he blended into the background and wasn't really noticed. When he did his GCSEs he beavered away and got mostly A* with a few A grades, and when he went into 6th form he started to get pressure to apply for Oxbridge.
He decided to apply just to see how he would get on, and he got an interview but no offer. In his A levels he got all A stars which is higher than the standard Oxford offer for his subject...so I guess that means he just wasn't Oxbridge material!
However, he is very happy at his RG uni and doing extremely well, so I can't see it affecting his life much!