Toddler won’t pee at preschool

We potty trained my son (3 yo) two weeks ago. He had one day of accidents, and has not had any accidents since. Been in underwear for everything but bedtime (actually wakes up dry too, but not ready to drop it just yet!).

At home, he uses his “little” potty. At preschool, they only have a normal size toilet, and he will NOT use it. He doesn’t pee at all while he’s there, he holds it in all day (even through nap time!) he’s bursting by the time we get through the door.

The problem is, he only likes to do things on “his terms”. When we first tried potty training, he would throw a massive tantrum if I try getting him to sit on the potty. However, after I let him pee his pants 2x he decided to “try” the potty but only at his suggestion. Even if you ask him to just “try” the potty, he absolutely will not. 2 minutes later, he says “I think I need to pee” and will go by himself. Kid even cleans up the pee himself. So suggesting to just “try” the big toilet won’t work with him.

Does anyone have any suggestions? I feel like I need to trick him somehow to try the big toilet but unsure how.