I was taught to apply carb heat during the downwind checks and leave it on until applying full power for the go around or touch and go or until clear of the runway.
However, one day when the wind was 14 knots straight across the runway and pretty gusty, not student solo weather in a 152, instead of scrubbing the lesson I chose to do some circuits with the instructor so as to practise cross wind landings.
I think I might have frightened him slightly on one of the attempts - he managed to go around OK, but made me turn the carb heat off just before landing for the rest of that trip so that he'd have a bit more power if he needed to do it again. So for him killing the carb heat just above the ground was not normal practice but was something you might want to do in bad weather.