Yami I am 8 - 10 years older than you (I am 25), back in the day there was a rule to focus on the lead demographic, I was lucky I attended a progressive school.
Having said that, about 5 min from my house I have SFX a catholic school and King David, a Jewish school they have to have police officers to keep the two schools apart on the bus or it would be a blood bath on both sides. It's not nice if you even live close to them as in the middle is a standard state school where my sister attended, before the bus she was harassed by Muslims and on the bus she was harassed by Jewish girls an boys (Before any one asks I put a stop to both sets of harassment) .
Talking right now as a Atheist I feel that they are all exclusionary.