Has anyone had their kid in the HISD pre-k 3 program? I have so many questions!!

My son will be 3 in July and starting pre k for 3 year olds in August. He has never been in daycare. I know he will love being around other kids. What do you think about it? Is it really all day? Do they really not help 3 year olds with bathroom time? What if they have an accident? What can I do to prepare my child? What are some tips? Thank you in advance!