Frustrated and in need of some advice please!

Hello fellow Mommy bloggers, I need some tips and fast! I am beyond frustrated with 2 aspects of potty training and hoping someone has some tips & great solutions? Sammy is for the most part potty trained during the day (still in pull up at night) and tells us when he needs to go, takes himself into potty, etc. I say most part b/c he won't go #2 in the potty! He did for about 2 to 3 months but now for most of the summer he has stopped and I am beyond tired of cleaning his little underwear. I have actually even had him help to clean them some hoping that would inspire him to go in the potty, no such luck. Any advice on the #2 issue?

The biggest issue however is related to school. They boy has quit going at school! I don't know what is going on in his little mind but he was fine and doing great in his old class and once they moved up to the new class he started having this problem. He basically holds it until naptime when they put a pull up on him, then goes in the pullup, then once big boy pants are back on he either has an accident later in afternoon or hold it until we come. At home though he is fine, no probs. Out in public & other people's houses, no problems either. This morning his teacher said they just don't have the time and resources to continue cleaning it and dealing with it each day so he needs to go back into pullups while there. AHHH!!! So expensive!!! I can't believe this. I agree with the teachers, I feel bad that they are having to deal with it each day and appreciate all the effort they have put in to helping him. I am just so frustrated with the whole thing. The kicker is I am one of his Sunday School teachers on Sunday mornings in the EXACT same classroom and he goes with no problems! When I took him in to check out the potty and have him go during school hours he wouldn't do it, even with me. I mentioned it when we were in the doctor for his tummy issues and she asked him about it, he told her he didn't like the potty because it was messy. His sweet teachers even said they would wipe it where he can see them do it before he goes (so ridiculous to take it to that level but we are desperate) but that didn't work. One teacher even brought in special chocolate for him and still nothing!

We have talked some about it and he only says he doesn't like it and won't use that one. Last night while we were playing outside he was pretending he was a lion trainer and working with Mickey, Minnie, Donald, and Goofy at a circus. He was running here and there with "Donald" and talking to him so I, being a psychologist, told him to take a break because Donald needed to go potty. I said "Tell Donald to go use your potty in your class it is right over there, see it?" and Sammy looked then found the imaginary potty and took Donald over to it but Donald couldn't use it. He said "oh no Mommy, Donald really doesn't like that potty, him hold it" and he kept on playing! Ugh! I don't get it.

So, anyone been through something like this?Any tips? I understand he will eventually learn and it needs time but I don't want to have to buy pullups again. He hates to wear them and thinks they are for babies so maybe forcing him to wear them at school will do the tick?

I welcome your input, thanks!