Do any NFL players go directly from high school? I think I've heard of a few NBA players that have come close and MLB has its own minor league system so they recruit directly from high school.
No, NFL has a gentleman's agreement with NCAA-FB. A highschool graduate would have to sit out 3[1] years before being eligible to tryout for the NFL. They could play in Arena football or CFL. Uni is the best path because you have competition and training.
[1] http://en.wikipedia.org/wiki/National_Football_League_draft#...