I've been on both sides of the fence.
I started out in a fabulous, local, very small public primary school. My parents decided halfway through, that they might try and see how I go in a private school, as their friend's son went there and they raved about it. I was a bright kid, and they figured maybe a public school would hold me back, despite the wonderful teachers at this particular school.
I spent one year at the private school, was bullied immensely, was as miserable as all heck. I hated it. And yes, it was a strongly religious school. My 'school swimming uniform' cost more than one year of school fees at the public school! My grades were ok, but I came home crying every day because I hated it so much.
Parents sent me back to public school for the rest of primary school, and then high school and I did extremely well!
I had friends who went to private schools, their parents paid a ridiculous amount of money to send them there, and only 2 out of the 7 friends ended up going on to University. The others still work in supermarkets, child care centres, take away shops etc. in their mid 20's.