The thing that I have found is it depends on the sport, your resourcefulness and luck...my son plays basketball...he's pretty good, but his HS team is average...although he starts varsity (he's 15), his real exposure occurs after the school's season is over. He plays on an AAU team out of Hartford and travels around the state and NE. His team is damn good and he sticks out like a sore thumb, a short, white, point guard...he loves his teammates and he loves the game, he's obsessed with it and he works hard at it.
Along the way we found out about exposure events, pay 40-50 bucks and play 3-5 games with about 90+ kids from all over the NE, there are scouting services and DII and DIII coaches there...well, the first one last fall, he got a small blurb on a recruiting service website and one about 3 weeks ago he got a major write up and was labeled a "real prospect"...after a game at a tournament last week, a DIII coach approached his coach about him, got all his information, a head coach from a prep school wants him to come out next week for a work out/evaluation. We know that none of this means anything right now, he needs to continue to develop...blah, blah, blah...but what I'm getting at is it's a tremendous amount of luck, being in the right place at the right time, meeting the right people...but most of all it's about exposure....you have to be seen, and for some sports that pretty tough unless your school is a major force in the state.