A.M.
I'm not sure if there is one as I think Kinder is pretty much recognized as a grade, where as preschool is more or less structured daycare. They start learning more and following a curriculum and schedule in kinder.
1st grade is only a year away and you don't want him behind.
School is only until 3 which I really don't condsider all day as the after school extended programs go until 6pm.
Anyway, I saw a question not too long ago about someone wanting to know if there really was a difference between a child who went to preschool and a child who went to daycare before kindergarten and she went on to ask if half day kinder would be ok if she wanted to save money on tuition. A school teacher replied this: "There's a very obvious difference between the kindergartners who did pre-school and those who were in a daycare environment. It is even greater once they enter 1st grade after a half-day program or an optional kindergarten. Full day kindergarten is based on time needed to actually teach the kids and prepare them for 1st grade. In a "normal" classroom you will have kids from every part of the spectrum when it comes to their ability to learn. Throw in the fact these are 5 year olds and most are new to a school environment and they still need LOTS of "teaching" for everything there just is not enough time to properly get them ready in a half day. Too much time is used fixing their shoes, going to the bathroom, getting their coats/jackets on to leave, getting backpacks done to leave, putting up coats/jackets when they arrive at school, getting things ready to learn, washing hands,snacks, etc."