Begin documenting behavior and conversations with parents as soon as you become aware that there is a serious problem. Discuss the situation with your principal. Most schools have a referral process already in place. Talk with parents, perhaps along with the principal. Have all written records handy in case they are needed.
Most schools have a special-services team of social worker, psychologist, and psychiatrist.
Others offer outside referral sources, although parents may prefer to take their child to another qualified person whom they have learned about through a family doctor, pediatrician or local mental health agency. Encourage parents to seek an individual who will work with them as well as with their child, and who will welcome input from the teacher. Recommend that children receive a thorough physical examination. If this has not been done recently, check if behaviors could be medically linked. In talking with parents, it's important to discourage them from blaming themselves.