"Actually, Hacker School is vocational and requires an "M" visa." This is not true. See my response elsewhere on HN (https://news.ycombinator.com/item?id=92657

"Actually, Hacker School is vocational and requires an "M" visa." This is not true. See my response elsewhere on HN (https://news.ycombinator.com/item?id=9265755 https://news.ycombinator.com/item?id=9265755), but the tl;dr is: We've confirmed with immigration lawyers that it's perfectly legitimate for people to come on visitor visas. A couple of people have had their visa requests denied (not because of anything specific to us but because of concerns that they would stay beyond 90 days), but no one has been rejected at the border, though some people have had a long and hard time explaining what "hacker" means to the border guards.