I went to a private school (high school only). I thoroughly enjoyed it. It had and still does have a good reputation. Students are taught respect for themselves, their peers and their elders (something that at lot of gen Y seem to be lacking!) I think I had more opportunities than some of my primary school friends didn't. My grade at school was a friendly bunch, and despite a few guys who were *********, everyone got on. There was no bullying or anything.
If you spoke to my sister your get a different story. She hated it. Was bullied by a girl who went on to be a school vice captain and no one believed her (because who could believe a vice captain could be a bully?!). Mum was furious. It depends on your kids really. My BIL is still in high school and I'm worried for him. He has been in the same private school since preschool and is very sheltered and his social skills aren't that great. I attribute this to his entire schooling being in the private system. Same with some of my friends. You could always pick the ones who had been at the school since preschool.