I might be going against the grain here but tbh I don't think the be all and end all is in the teaching and selection.
Personally speaking and in the case of my dc, if they are interested they/we go into a subject in greater depth by reading independently, going to museums, Googling it etc, talking about it.
I did not need my parents forking out a fortune for a private education for academic purposes, I was more than capable of getting a text book and learning what I needed from it and getting straight As. As far as I'm concerned, my dc do not need it either. I'd rather send money via direct debit to the NSPCC than spend it on my dc.
I was in my element at college where I was able to sit in the library being able to peruse 40 books (all the books on the reading list!)per tutorial. It was hard at first because I had to look up many of the words in the dictionary as my own family were far from being intellectual and we were not allowed boks at home.
Luckily, my own dc do not have that obstacle to learning.
Lots of little state primaries provide a warm, nurturing environment to learning, with mixed ages and streamed according to ability as far as which table they are sitting at.
I think you will find they are fabulous places to develop a love of learning.