As someone who went to a school where they did take Non-Orhtodox children
I can tell you the results, over 95% of the relgious kids stayed religious. A few obviously left, but I have no idea if that was because they met the non-relgious kids or not, I am sure some left for that reason.
about 20-30% of the non-relgious kids are now religous which to me is a pretty good success rate given the circumstances. If a school refuses to take a non-relgious kid and they good to public school, I can pretty much gurantee the likelyhood they will be relgious is alot less than 20-30%
But in general there was a net gain evne if there was some loss