Ok now this is the interesting part: the magic foundation.

After Dumbledore had made Hogwarts, he admitted the sons or daughters of his brothers and sisters to be staff members for Hogwarts. One of them was Professor McGonagall. They became great friends and trusted each other greatly. But when Dunbledore had found young Tom Riddle, everything had changed. He can speak Parseltongue, Dumbledore thought every night as the rain poured outside. It was Tom Riddle that had broken the trust between him and everyone else. Once Tom Riddle left to become Voldemort, Harry Potter had arrived years later.