I think you should ask to see a day of the co-op. I'd really consider it if I were close.... well.... of course... that's my thought.... (and I'm a conservative Christian) BUT, it really is different, depending on what your group believes. My daughter is the spend the night with friends.... be silly... stay up all night and watch some movies... play games.... etc.. She's 12 so I'm ok with that.
Our ballet class for her, until this year, was all hs girls.... no one really invited her over.... or did outside things... (except a couple of times in like...8 years) they are more the "stay with parents" kind of kids.
;)