hi grinity,
though my kids are too young and we don't have personal experience with it, i have been intrigued with IB international baccauleareate (my kid could spell it!) schools. I have a friend-of-a-friend whose child goes to Atlantic College in Wales. There is one in Pennsylvania called the George School http://www.georgeschool.org/Academics.aspx
I like the international flair, very appealing in the "cookie cutter" world that education is around here. As far as academic rigor, they do have AP classes, and i read somewhere that an IB diploma is considered higher than an A-level in Europe. Happy hunting!
irene