***I am acting as a child who has dealt with bullying and not a parent***
My first suggestion would be to move your question to the Parent's Discussion forum. You're going to get a lot better advice there. I was lucky enough not to get bullied all that much. I attribute that to the fact that I seem to exude an air of "likeable". However that's not to say I didn't have issues with bullying. My suggestions to you as a parent are to be watchful of how you're child is acting and how other children are reacting to him. If he is very severe, i.e lower functioning Autistic or Aspie, or if he is very sensitive be open to other methods of schooling. I don't want to suggest that you jump to a private school or homeschooling immediately because some children with ASDs handle public school quite well. I just want to emphasize that these are options if there is no other fix. If your child mentions that he is being bullied, ask him why the children are bullying him, provided he can tell. If it's something simple that can be solved by a change in behavior, there are literally thousands of resources out there to help parents with kids on the spectrum teach said children skills for dealing with social interaction. If the bullying is not an easy fix, i.e the kids just don't like him or feel like picking on someone, talk to the principle and the administrators. It might not do you a lick of good, but it's worth a try. Be sure to help your child keep his self esteem up. Remind him that he/she is special and nothing the bullies might say will change that. Emphasize his strengths and serve your duty as a parent by giving him a shoulder to cry on. Don't ever reinforce the negative garbage that they spew at him/her. If all else fails, don't keep your child in the school. Don't ever assume that they'll "buckle down and learn to bear it". It might look like it on the outside, but what you're seeing is permanent damage to the child's self esteem and childhood depression. Don't ever promote bullying! No matter what happens, you must never force your child to deal with the problems. Look up the forum post on cyber bullying from rather recently and you'll see just how insane it is to promote bullying. Lastly, if things progress too far just pull your child out. It can't hurt to let him learn in a less stressful environment. Good luck.