On the Other Hand …
Kids who are past the preschool and kindergarten years are old enough to understand that some behaviors are acceptable at school and others aren't. If you receive a call from your child's school about her behavior, take an honest look at how your child is acting out. Hostile nonverbal cues (such as smacking and making faces at other students or attempting to dominate them by glaring at them or stepping into their personal space) need to be addressed. These types of behaviors aren't simply a means of innocent expression, they're indicative of a mean streak that's going to land her in hot water again and again. Just as importantly, these nonverbal cues are also likely to lead to social isolation at some point. (Who wants to play with someone who's going to haul off and hit you?)
Kids Will Be Kids
You've heard it a hundred times: bullies tend to be insecure people who treat other people badly to bolster their own egos. A child who uses hostile or inappropriate nonverbal gestures can often be led to express herself in another way, whether that's verbally, artistically, or athletically. Don't expect the child to take the lead here; she'll need guidance and nurturing to find her niche. Once she learns to channel that energy and/or anxiety into an activity that she enjoys, reassess her nonverbal cues. If you find that she's still displaying unfriendly body language (old habits die hard, after all), teach her to use nonverbal cues that send out a positive vibe (such as smiling, keeping her hands to herself, and respecting others' personal space).
In the end, it's important for parents and caregivers to remember that kids are blank canvases. They're just beginning to learn life's lessons, and a lot of what they'll discover will come from the nonverbal communication they see in their parents, teachers, siblings, friends, and even strangers. Although these sources of information are wide and varied, there's one thing every child needs: to feel safe and secure at every age and every stage of life (even when they're disagreeable toddlers … or teenagers). You can help your child to develop a sense of confidence — which will show up in his body language — by making sure that your gestures send a message of love and nurturing.