Can you "schedule" a break or two with the teacher ahead of time, so that he doesn't have to ask each time?

Schedule it. Put it on his visual schedule so he knows and so do the staff. Find out if there is a particular time when it is happening....after eating, playing, stressfull new things... I like the watch idea too!!

can he made a signal? maybe 1 means bathroom. the teacher says ok by shaking her head and then he goes

Thanks everyone for the feedback. CBP I never considered that he may not like "foreign" bathrooms. Now that you've said that he doesn't really like going to the bathroom when we're out whether it's a BM or just pee. Scheduling a break time may work as well. They have tried the non-verbal laminates as well, and all he'd have to do is raise the picture, I don't think he's really used that at all. I think the bigger problem is he goes so far into himself off when he is at school and doesn't talk or interact with anyone - it's almost as if he's afraid. He's never wet himself it's just the BM's. His teacher and therapists are aware of the situation and they are the ones that put the social stories and cards into place. We;ll just keep trying things until we get it right. Thanks again for the feedback!

Have you looked into encopresis as a possibility?