On the paying for a better childhood rather than a better future salary - I think this is true, though I also think "better" is subjective.
My parents would have sent us to single sex grammar schools by preference, but didn't feel strongly enough to actually remain in an area with a grammar school system and moved when we were primary age, and put us into private.
They didn't take into account that the move + school combination actually made us outsiders in the small community they moved to, and although I enjoyed school itself I'm not sure that feeling (and bring treated) like an outsider around local children/ teens was necessarily a better childhood.
There were lots of odd things about my school though I was happy in my rather disconnected from the world bubble with my friends. I learnt later that there was horrible bullying in other year groups, and there were a much higher than average level of eating disorders and suicide attempts (luckily none successful and probably not completely intended to be) in my year group. Some actually quite dangerous things happened at night which I'm quite sure nobody told their parents about and school only told the pupil's own parents if a pupil was suspended (or expelled obviously - and we had several expulsions just within my year group, the same in most years).
Like most things about secondary children's lives, parents have a better idea about what's going on if they had similar experiences. Children and teens just automatically keep some things from their parents and tell their parents what their parents want to hear.
I was actually quite disruptive myself in some lessons 😳 but I got good grades and it was largely tolerated. I taught in state schools myself later and it was a different type of bad behaviour - certainly I was never directly rude to a teacher but we pulled a lot of whole class "pranks" which completely made a mockery of whole lessons or even series of non core lessons (running gags which totally took over)... The disruption was actually pretty significant but very different to the constant talking or occasional actual shouting and swearing and throwing things which I encountered in some state school classes.