V.B.
I guess every kid is different in the amount of sleep they need and I haven't ever had my kids in daycare, but my son is 18 months old and is just now transitioning to one nap. He still gets tired in the morning and I have to get him over that hump and push him until after lunch time in order to keep him on one nap. Otherwise, he's tired by mid morning and still likes to sleep. Sometimes he can catch a quick catnap in the car or something and that will hold him off until naptime in the afternoon.
I think 11 months is too young for a one nap schedule, personally, but again, each kid is different. Do you have any say in what happens with the schedule at his school? If so, I would ask that he be allowed 2 naps for at least a few more months. I guess you could always see how he adjusts to it and go from there. Good luck...that is a tough one. So sorry you're dealing with that!