C.Z.
Honestly, it could be just timing. My oldest never displayed any aggressive tendencies but he didn't start pre-school until he was 4, but he VERY much preferred to play by himself, not so much preferred as was afraid to play with other kids (unless they were older, or it was one on one. He wouldn't go near a playground if their were other kids, no McDonald's playlands or anything of the sort. His preschool teacher was really worried that he had some degree of sensory disorder, he did great in school but just wasn't comfortable in groups of kids, it was like overload for him. Last year he started kindergarten and he was having trouble playing with the kids on the playground, I started out by telling him he didn't have to play with anyone but I wanted him to go out and go down the slide three times, he was in tears "I can't" well the next day he came home, "I didn't go down 3 times but I went down once!" and then I lavished praise on him for his accomplishment. It has taken time and little steps, we did a cooking class, a little gym class, and one semester of soccer, not all at the same time, just little things here and there to help his comfort level in social settings. He just started 1st grade this week and for the FIRST time, he's really done great, and part of that is the little things we've done along the way but part of it is just age. Good luck