Someone once told me that, in most cases, your son's high school coach won't be instrumental is getting your child a college offer, but he could definitely keep your child from getting an offer.
On another note, my son's basketball coach told the parents that for the past several years he had spent a lot of time coaching attitude, and that last year that would stop. He wanted all of his players to have a good attitude so that he could coach basketball and not attitude. The kid with the most talent and the worst attitude just announced that he was transferring due to lack of playing time.