I was all girls for 7-10 (high school) and co ed for 11-12 (college).

IMHO all girls can be very very b*tchy and not a nice place but I know girls who have been in that situation and had a great time. For me my co ed years were much easier to handle and less stressful.

I really don't see the need for single sexed schools, each to their own but life isn't all girls or all boys. At uni it will be co ed, at work it will be the same and I think its better they get use to being around "normal" situations.

Some girls I went to school with who went from all girls to co ed went off the rails and didn't handle it well but of course others fitted in easily.