S.C.
My son (now eight) was also transitioned into full day preschool when he was three. I feared that a full day might be too long for him too, since he previously had been at home with me. While he did go to a playgroup 2 days a week and receive services at home I thought a full day "working" might be too much for him. I decided to start him off just going half days. The school wasn't thrilled with idea at first but I thought he would need to build up to it. After about 4 months I let him go full time. My (and his) experience was wonderful. He was tired at first but he did get used to the routine. I thought the entire program was so beneficial for him. He did learn a lot of skills that I wouldn't have been able to teach him at home - and he loved his new friends. And a little side note - when he started kindergarden the transition was seamless becuase he was already used to going to full day school. Good luck!