What's the criteria for "first generation college" as a hook?

My friend will attend Williams and his hook was that he is first generation. He wrote about it in his common app essay and under the parents’ education section, he specified that they did not attend college (not even comm.college). To the OP’s question, I guess it could be a don’t ask-don’t tell situation if a grandparent has a college degree, best left up to ethics.