Having been privately educated at secondary level (father in the military) I always wanted a local school, that we could walk to, with friends within easy reach for my children.
We had this for DS1 (luckily as we couldnt afford private then anyway) and he did fairly well getting L5 SATs in Y6. However, when it came to selecting secondary school we felt that a local independent one was a better fit for him and, as our financial circumstances had changed, he sat the entrance exam and got in.
Then we had DS2 (7 year age gap). Although we could afford to send him to the prep school attached to DS1's school we wanted the same experience for him, certainly at primary level, that DS1 had.
Unfortunately, the headmaster had changed, there was alot of disruption with supply teachers etc and DS2 struggled academically with a few things that weren't helped by the large class size. It also just didnt have the same feel to it as when DS1 attended. So we moved him to the prep school where he is now doing really well.
I could've done what a few of my friends had, moved him to a smaller, village school (the state primary he was at was a big school, 3 form entry) but logistically it wouldnt really have worked for us.