Uh-oh. Your 4-year-old is playing king of the playground—pushing and grabbing, hoarding toys—and reducing classmates to tears, reports his teacher. Naturally, you’re cringing. Why is your once-docile child now so hostile? Don’t fret just yet. “It’s pretty common for kids to be aggressive at this age, largely because they’re trying to figure out how to socialize with others,” says Laura Hanish, PhD, an associate professor of child development at Arizona State University in Tempe. Preschoolers are learning how to play with peers, enter into groups and share materials, and most children don’t yet have strategies for problem solving.

Still, if a child’s aggression or anger is intense and frequent, it can lead to fewer playmates—now and later, according to a recent study led by Dr. Hanish. This is true for both boys and girls. “Due to temperament, some children are better able to regulate their behaviors and emotions, while others are more emotional and reactive and get angry more quickly,” she explains. Plus, factors like excess stress or exposure to aggressive behaviors at home or in the media can exacerbate a child’s aggressive tendencies. “Children who see aggression used as a strategy are going to imitate these behaviors,” Dr. Hanish adds.

So parents have to be particularly mindful about shaping and guiding their preschool-age child’s positive social behavior. Be clear about appropriate limits on interaction—no grabbing, hitting, pushing and so on—and when these rules are broken, impose consequences like short time-outs or removal of the tug-of-war toy. Remember that spanking or hostility on your part models aggression rather than quells it. And catch your child being good: Encouraging words for sharing, caring and waiting their turn can help kids channel aggression the right way and encourage friendships. “Teach him how to solve conflicts and problems by using his words, and model positive ways of dealing with conflict he can mimic,” says Dr. Hanish. For example, when you and your spouse disagree on something, calmly discuss a compromise—and show your friendship—in front of your child. As Dr. Hanish puts it, “Focusing on the positive really works.”

Taming Your Preschooler

Your child can develop good habits once he learns to channel his aggression, says Dr. Laura Hanish. She suggests:

Go over a conflict resolution together, and encourage him to talk about his emotions—anger, frustration, disappointment.

Monitor Media intake. Kids who see aggression on screen are more apt to see it as acceptable behavior. Limit viewing time to no more than an hour a day, and make sure your child is watching programs that exemplify good conduct.

Involve other people. Enlist caregivers and grandparents to model positive actions.