T.G.
I agree with taking away pull ups. Also, I would tell day are to have him try every 20 minutes to get him to sit on potty. Eventually increase the time. But it will remind him to try and it will also make him want to go when he has to so because then he can get up and go back to playing. Also. If he has an accident with peeing I would pay no attn to it, just Hans him new clothes and tell him to go change. We did that with my daughter at three when she regressed. When she had to change with noone paying attn she it the idea. If school doesn't help with this then talk to the director or find a new one. You need their support. Good luck