I went to a quaker school from 7th-12th grade. There is so much variation from school to school. Is there something in particular you have questions about?
My school is very old (over 200 yrs old) and in some ways a very typical prep school...but with a peace-lovin' bent if that makes sense. Excellent academics, but somewhat high-pressure. Lots of discussion and awareness of social justice issues. I understand that many Quaker schools are far crunchier than the one I attended, with much less emphasis on grades.
I'm Quaker, fwiw, but most of my classmates were not, and apart from once weekly meeting for worship, the religious aspect was pretty minimal.
Let me know if there are any particular questions I can answer.