I meant to post this last week when it happened but totally forgot. Last Tuesday (Feb. 5), Harmon used the potty at school! It was the first time he's gone at school and we are so proud of him. Evidently, he was pretty proud of himself too because he talked about it all damn day (per his daily activities sheet at left).
He's been going at home on a semi-consistent basis since the Christmas break. I think he was hesitant to go at school because his teachers likely won't spend 45 minutes reading 20 books while he sits there (like we had been doing). Recently, though, we moved him from the potty to the real toilet (with the adapted seat) and cut out the books. He seems to go faster now and maybe that's why he went at school. Whatever the reason, we were glad there was some progress.
His teachers have told us that most of the kids in his class are using the potty consistently now and, while he's not there yet, this can only benefit him. We also need to keep in mind that he is THE youngest kid in his class so we just can't expect him to do what all the older kids are doing. As with most things, it will all come in time.