First of all, if you are being physically abused, you should immediately call 911 at the time of the abuse. You should also tell an adult that you trust (like a teacher, doctor, police, relative, etc.) about the abuse. You should also call Child Protective Services at 1-888-767-2445 and Childhelp at 1-800-422-4453.

But, if you are being physically abused and you cannot run away or get help to stop the abuse, and the only way to protect yourself from on-going abuse is to become physical, then seld-defense it is allowed by law (as long as you only use as much physical force needed to stop the abuse and no more - if you use more physical force than needed to defend yourself, then you could be charged with abuse). (ARS 13-404)