I've noticed that to be true in this area as well. Now not all are that way; I've got a friend from school who went to Catholic school, and she's extremely nice; our neighbors sent their daughter to Catholic school and they are great neighbors, etc., but it does seem to be a general attitude. Our neighbors' daughter had to switch schools because she was being horribly bullied. Also noticed when I was in high school that private school kids treated public school kids like they were beneath them (Again, not true of all of them, but a general attitude).
I guess if you're going to send your kids to a private school of any kind, just like colleges, it's important to visit the school, determine what kind of people go there, and make sure that it's the right fit. I went to public school. The public schools around here are very good. Considering I got a large scholarship to my college and came in with 15 credits, I'd say my previous schools did a decent job. Also, several students went to Ivy League schools. So not too shabby. All depends.