aggression is a normal part of a child's development. Lots of children this age grab toys from classmates, hit, kick or scream themselves blue in the face from time to time.
Other triggers may have more to do with frustration. After all, your child is learning a lot of new skills, from using scissors to speaking in complex sentences. He can easily become frustrated with everything he's trying to learn and end up pouncing on a playmate. If he's going to preschool for the first time, he's also getting used to being away from home. If he feels resentful or neglected on top of everything else, he might just retaliate by shoving the child who won't get out of his way.
The good news is your child will eventually grow out of his aggressive behaviour as he discovers how to use words instead of fists and feet to solve his problems.
It's best to let him know instantly when he's done something wrong. Remove him from the situation for a brief time-out – for a 4 year old, three or four minutes is enough. The idea is for him to connect his behaviour with the consequence and to work out that if he hits or bites, he'll miss out on the fun. No matter how angry you are with him, try not to shout, hit or tell him that he's naughty. Rather than getting him to change his behaviour, this simply teaches him that verbal and physical aggression are acceptable when he's angry. Instead, set a good example by controlling your temper and calmly pulling him out of the situation.
http://www.babycentre.co.uk/a1021981/aggression-why-it-happens-and-what-to-do-about-it-ages-3-to-4
Read more
