Did he have separation anxiety when he finally went to school? Our 3 year old son does not like to be out of our presence for more than a few minutes although he is otherwise happy and healthy (knock on wood). I've been wondering how he will be able to transition to go to school.
My daughter had no pre-school. She walked into kindergarten, and didn't even bother saying good-bye to Mommy. *I* was the one who was traumatized. :)
I read all the time that homeschooled children (I'll extend this to young children raised at home) are very comfortable with adults. Socialization with other children now would be a good idea. This could just be your child's personality, more than the setting (more nature than nurture).
My 3 year old daughter had the same issue. We used to take her to Little Gym for classes and she would spend the first 10 minutes clinging to her mother, who had to accompany her inside. But on her first day of Pre-K, the teacher kept her so engaged, she forgot about us. The secret is to avoid the "departing ritual". When they are first distracted, duck out of sight. If a teacher is engaging, the child will forget about the parents. Perhaps you've tried this and it didn't work. In any case best of luck to you.
trying getting your kid somewhere once a week or so where you can be right there if you're rally needed, but out of sight. any community type thing is good; sports, reading time, if your church has a "nursery" or children's group, those are really good.
you could also see if there's a daycare nearby, find out when they goto the park and see if its ok to join them once a week or so.
"I've been wondering how he will be able to transition to go to school."
There's a solution to that: don't send them to school (i.e., homeschool) until they are ready. Some kids take longer than others to get ready.