Call the school to find out if any procedures have been put in to place to deal with bullying. If there are existing procedures, you will want to follow them.
Find out what your state's anti-bullying laws are. You can call your local government, or you can check BullyingPolice.org and click on your state. This information will give you guidelines on what you can do about the bullying, as well as what legal actions you can take if it comes to that.
Record every incidence of bullying. Of course you don't want to wait to take action, but in the meantime you need to write down everything about the bullying incident in as much detail as you can. If physical bullying occurred, take pictures of any bodily injury.
Contact the child's teacher if the incident took place in the classroom. Give the teacher a chance to handle the situation. You may want to suggest the teacher call a meeting between the parents of the bully and yourself.
Notify the principal if the teacher fails to take action. You may go straight to the principal if the bullying is not occurring in the classroom. For example, the bullying may have taken place on the playground during recess or in the hallway in between classes.
Send a certified letter to the school board if the principal has not taken action to stop the bullying. Make sure you include a copy of your detailed accounts of the bullying, as well as any conversations you had with the teachers and principal. Keep a copy of the certified letter for your records.
Call the police if the bullying has become physical and the school is not handling the situation.