Ah, so difficult. Does she have either an IEP or 504 plan at her school? If not, I'd inquire about this. My son did not qualify for an IEP (individual education plan) because your academic performance has to be impacted. But, he has a diagnosis of sensory integration disorder (adhd's neurological cousin) which impacted other things so a 504 plan was granted. This allows him various accommodations. Now, we didn't put this into place until about 4th grade and were able to work with his teachers to get a plan that really addressed his needs (he has movement breaks, extra time on tests or homework, preferential seating, etc.). Now, I guess a good question is about the issues with going to the bathroom. Does she got that much at home? Everything okay with her bladder? The number cards are probably what most kids would need and then some. Why does she need more? Perhaps a system of having her hold ONE card back to save just in case may help. She's only 5 though so not sure she'd really conceptualize this. But is there a reason she goes to the bathroom more than other kids or would need more cards than them? What does he teacher say that might help?
It's a huge adjustment for some kids to fit into the classroom setting (especially adhd kids or sensory kids like my son). And I do agree that nipping her tantrums at school in the bud is essential. Not JUST because it is disruptive but because other kids will start to notice this and become distant from her. What I did for my son w as I talked about being a good friend to others. If he was having a meltdown or being loud, he wasn't being a good friend because the other kids needed to focus. It worked for my son.
Is she taking medication? Can they do a reward system for her at school? What other things do her parents do for her like a regimen of activity outside of school (physical activity) which is known to help adhd?
I agree with Specialmom. sorry I did not respond sooner as this is dear to my heart as a retired elementary school principal. Essentially, a teacher can not refuse to let a child go to the bathroom.
But what is important here is the why? She is under a lot of stress and that is possibly why the trips. Anything that can be done to release that stress will help. In fact, if she is still having these problems, either her mom or you should visit the classroom and see what is going on.
I am also curious if she has come home with wet underwear? If not, somebody is letting her go to the bathroom or she really does not need to go - but does need to get out of the room due to the stress. So, there are - as Specialmom suggested several thing possibly going on here.