BEagle, no offence taken, you may be right about a finals acronym being OTT. It worked ok (like I said, the students liked it and could remember it) but I'm all for learning a better way.
One other way of ensuring you put the carb heat off (in a C152 at least) is to tell the students ALWAYS to advance the throttle with their thumb stuck out at right angles- that way it catches the carb heat lever and pushes it in as well. That way fulll power WILL be available on the go-round (unless you've got the rich cut problem mentioned above, of course). Doesn't solve the dust ingestion problem, though.