Many young children do not know how to take a stand and need to be protected. Use a buddy system by pairing them up with an outgoing classmate. Parents should avoid confronting the bully themselves. This only proves to the bully that the victim is indeed weak making the youngster an even more attractive target. Speaking to the bully's parents is also not very productive since they usually have little involvement with their child anyway.
All children lose when aggression is tolerated, the bullies, the victims, and the bystanders.
Parents need to be receptive to their child's accounts of violence and report them to school authorities. Insist that the school do whatever necessary to guarantee their child's safety. Furthermore, there should be no retaliation because the youngster reported the bully. If the school refuses to take a stand, consider more drastic measures such as transferring the child to another school, reporting the incident to the police, or filing a lawsuit against the school and the bully's parents. Aggressive children need to be taught that anger is okay, but lashing out is the wrong way to handle it.