Thanks for the suggestions everyone. Unfortunately, DS doesn't like using the bathroom anywhere. I do believe he dislikes public bathrooms the most, but will avoid going to the bathroom at home too. The other day he blatantly lied about having gone already to avoid having to go when he got up in the morning. When I caught him in his lie, his only explanation was "I don't like to go to the bathroom".
Since he has no problem lying about using the bathroom, I don't think a reward system will work as we'd have no real way to monitor this at school. My mother actually tried to bribe him with money, first paying him for each time he used the bathroom and then changing it to pay him for each day he was accident free. She started this while we were on vacation together and didn't ask me about it beforehand. I let her do it knowing vacation would soon be over, but then she tried to rope me into continuing it at home. I can tell you that neither scheme worked. One of the weeks she paid him for accident-free days, he had accidents 5 out of 7 days, a record for him to this day.
He did have an issue with loud sounds when he was younger and probably as a result will rarely flush the toilet. We've tried to get him to change this habit, but have had little success, so have chosen not to make it a big deal at the moment. At home, or if we're out together, DH or I usually go in after him and flush. While we'd love for him to flush at a public restroom, we'd settle for him not having an accident and forgetting to flush...
We go back to the OT today for his first therapy session and will hopefully get some ideas for his sensory diet. It's hard to know whether he is lying about not knowing he has to go and not realizing he had an accident, or whether he really is that oblivious.
Wow, he sounds so much like my DS! Rewards don't work, he doesn't seem to even recognize when he has to go, and frequently doesn't seem to care/notice if he is wet. We have mostly accident free days but only because we enforce that he has to use the toilet before doing something or he gets timeout in his room. Even then he will just goof off in the bathroom - for a good while most of his accidents actually happened IN the bathroom while he was goofing off and not using the toilet.
