Ania,
Regarding The Think Summer Institute--
My then 13 yo son attended Think last summer, and it was wonderful. I cannot say enough about this excellent program. Outstanding, fantastic, the best anywhere. My son is not exactly a teacher pleaser, and he had always been in the regular classroom until Think. He matured in many ways, learned study skills for the first time in his life, and met mental peers. It changed his life and showed him that education was interesting and fun. By the way, since attending Think's Chemistry Class, my son has wanted to be a chemist. Think's Chem Professor was the most inspiring teacher my son ever had--exceptional.
I do not think you can go wrong with anything Davidson Institute does. They are first class.