It's been three days and your son has made a major switch. How about giving him and his teachers a chance to get to know each other before switching yet again?
They might be trying to put him down for nap at his usual time but he might be resisting. Should they just let him hang out in the crib, screaming and crying, or should they pick him up, console him, and try again later? The old school had a nice routine that your son followed but now he is in a different environment and everyone is adjusting, so give it time.
On the flip side, our son was recently moved up to the toddler room where they take one nap a day. At school he will nap 3 hours at a time and when we have him in the evening, he is so pleasant and happy. On the weekends? Forget it! We adhere to the feeding/eating schedule that he follows at school but he resists it entirely. He's more used to the school environment/schedule than the home schedule so we take what we can get on the weekends even if it isn't exactly on schedule.
Be patient and try not to micromanage. Yes, you know your child best but remember that these people have worked with hundreds if not thousands of babies and have plenty of expertise when it comes to helping babies transition to a new place.