Hello Mama,
It sounds to me as if your little guy doesn't know how to act around others. I'm not sure if he is in a preschool program or not, but kids do much more than just play for a couple hours.
The preschool age range is a time to learn how to behave in social situations. A preschooler will watch other kids and interact, making friends. Preschoolers are very social and peer dependant, because it's a natural part of their development.
I would suggest enrolling him in a preschool program, (if he isn't already). If he is in preschool, ask the teacher how his social development has progressed and see if there are any issues that need addressing. Alsp, set-up more play dates to increase socialization at home. Go to the park more so he learns how to interact with new children too.
I bet you'll see a huge difference once he learns some social cues. A well socialized preschooler will be less likely to be a "follower" in grade school.
Good Luck
R.