I think it is really common for kids to want to stay home. My DD4 only goes to school a few hours a day, three days a week, and never wants to go to school in the morning. She always says she would rather stay home. I usually just ponder out loud to myself what snack she will miss, and that is enough to get her to school.
More important--she is happy at school. She is upset to leave early when I pick her up before the end of her day.
My DD is very similar to your DS except that she socially immature or delayed. So, I do feel like she is challenged socially. She is in a strictly play based school. And, she is probably more angsty by nature. So, yeah, she might wax on about school being boring, but she will do this about everything. (I have heard that four and five can be angsty.)
I love that there are no academics at her preschool, but I do worry a little about next year.
