I wouldn't drop the nap hard- I'd slowly work up to shorter and shorter naps (hopefully his school will work with you on this). My son started napping again after he started preschool (mornings) at 3yo- he had given up naps at home at 2yo, like his sister. I imagine she'll be napping again when she starts next month.
But, he'd given the naps up again by 3.5-ish, and even while he was napping, we could only go an hour long at most before it would destroy his night sleep.