Old school I consider more to be '68/'69 with the Hammond and 2 drummers.
This was '72/'73 middle[jr high] school.
One of the few places I've been where people didn't just drop their empty cups on the ground - They cared to keep the dance floor clean, was really nice.
I don't and have never gotten why people do this at any concert. I'm as guilty as they come for setting a beverage in a corner or in a small nook, only to wander off and forget to grab it. But I've never finished one on the dance floor and just dropped it at everyone's feet. Seems absurd to me. No respect.