At ds' preschool, nap is optional. You put them on a list if you want them to nap. Otherwise there's no nap. It's a large preschool & actually offers kindergarten & 1st grade, plus it is open from 7:30 to 5:30 for working parents. Maybe b/c of the large size & diverse ages?? Not sure, but nap or no nap is up to the parents, although they will send a kid for a nap if he or she is falling asleep.
At the daycare we used, no, but kids move on from there at around 3.