I'd definitely recommend a USSA-affiliated mountain team over a high school team. The latter typically has you "racing" on courses at Blue Hills, Bradford, or the Wachusett NASTAR hill, with apparently meager coaching and skills improvement.
The Wachusett program is very professional -- I've seen some of their newbie racers, and their progression is impressive:http://www.wachusettmountainraceteam.com/
They had been having trouble last year replacing their full-time Head Coach, but now they've landed the former New Hampton School Head Coach - wow!
I believe they have varying levels of committment too. So it's not like you necessarily have to traverse the various highways and byways of New England each weekend.
The other strong jr race program relatively close to Boston is Pats Peak:http://www.patspeakracing.org
Beyond that, you're looking at much longer drives.
(Well, Crotched is back, but I don't think their race program is back in its pre-closure form yet.)
By contrast, a single racing-oriented lesson would probably consist of a few runs on a near-horizontal NASTAR course with some random pointers. (And the evening Wachusett race league is adults only.) But you could get lucky and find a ski instructor with a racing background who could set a real course.