Interesting post. My D, a college freshman, had finding PG people in a challenging environment at the top of her criteria list. Her final three choices were U of Chicago, Swarthmore, and Harvey Mudd. She is happily working her tail off and hanging out with bright people and bright professors at Mudd. Other schools that seem like they could have met her criteria: Harvard, Yale, Stanford, Caltech, and MIT. Certainly other schools have significant numbers of gifted students and challenging courses, but none except those seemed really immersed in the culture and challenges she wanted.