To get fired for substance-related offenses, we must assume that they were actually perpetrating such offenses (in most cases).
If those rules exist, then they must exist for a reason.
The camp I went to (@11 & 12 yo) did not have any drug problem but the counselors were a bit on the cool side. They were the types that just might pass around drugs if they had the opportunity. They were a bit hostile, too. One time my hiking group got lost in the woods, and we missed dinner. They gave us some cans of food, but no can opener. They didn't care that we just went hungry that night -- it was a joke to them. Lots of small similar incidents occurred. My sister fell and cut her head on a rock (but not a terribly serious injury). My parents found out from me! I wrote home that day that I had visited her in the infirmary. The counselors just weren't quite trustworthy. It is out-of-business now, probably sued out. But the camp had a wonderful rep and most people loved it and considered it "family." Go figure.
Of course, today's camps are much more lawsuit conscious, but still, should parents trust anyone who wants to take charge of their children for a prolonged period of time without any compelling reason? After all, outdoor sports are available anywhere these days. JMO: Seems likely that the "partying" started at the camp.