My son was almost 3 when he was trained, he is the youngest of 4, and what we finally did was start telling him when we were going to potty. Everyone did this. My husband and oldest son would take him to the bathroom with them and let him see them doing it. Eventually he caught on that eeryone else in the house is doing this except me. And he wanted to do it too. He never sat on the potty, but he did what the big boys were doing and never een wets the bed. (knock on wood) maybe what he is seeing at preschool is the other kids telling that they have to go potty and he wants to do what everyone else is doing?
Hope this helps
Melissa
Dirty Drawers

have u try to use cheerios they work to help him do it standing maybe thats the deal