DS not at a selective high school (yet) but this year he changed from a "mainstream private" where he was far and above the smartest kid to a specialised g&t primary school.
It was a rude shock for him to start with lol He is still in the top groups...but not the top student. After about a week we had a chat about it and he was a bit concerned but with some gentle reassurance that I didn't care about best in the class but that he was doing his best...he settled.
Anyway, now in Term 4 and he is loving it. Great group of friends, no more bullying, great confidence, less arrogance and he is doing fantastically and will be on track for selection for high school in a few years. having genuine peers around him, has been amazing.
Also, as a parent..it has been awesome. No more catty comments and nastiness about him, not 1 call to the office all year (it was weekly at the old school) and a huge stress reduction. He has gone from a child so anxious that I had to remove him from school for 6 months to a child that LOVES school and looks forward to going each and every day.