Here's a lovely interview with an alumnus of the Shippensburg Adventure Game Camp, a residential D&D camp for 10-17 year olds held at Shippensburg College (now Shippensburg University) in Pennsylvania. Campers played a series of rotating adventures in aged-grouped parties, with the councillors comparing notes behind the scenes to keep all the groups in synch and to ensure maximum fun and mayhem for all the players. They unwound with improv games.
I attended a D&D day camp around this time, 1983 or so, at Harbourfront in Toronto. We painted lead miniatures (I still love doing this) and had guest-lectures from medieval weapons freaks, a ninjitsu master, and a science fiction writer named Edward Llewellyn, who was the first published sf writer I ever met. He signed a copy of one of his books for me and I obsessively sought out and read his entire oeuvre. And of course we played lots of D&D. I still remember that as one of the most fun summer activities I ever got to participate in.
Shippensburg Adventure Game Camp ran in the summers of 1981 through 1985. There were two one-week sessions, each Sunday evening through Friday afternoon. I found out about it because the teacher we had convinced to sponsor the school D&D group got a flier for it when it was first organized.
Campers were divided into different gaming groups at the beginning of the week, with councilors doubling as DMs. There were morning lectures (seriously) with gaming in the afternoon. All the groups played through the same adventure, written specifically for the camp. It wasn't an actual tournament, but each group pretty much tried to get as far as possible before the end of the week — a slightly rigged process as I found out once I became a councilor.
The same campers could come sign up for both weeks, but obviously that wasn't the intention because they'd be playing in the same adventure twice.
There were a lot of other summer camps going on at the Shippensburg campus at the same time: baseball, tennis, cheerleading, etc. Everybody stayed in the dorms, with different buildings for different camp groups, but lectures and afternoon gaming were in other campus buildings.
(Thanks, Fipi Lele!)