This sounds like my child. I don't know exactly where you are located, but Parents as Teachers is a great organization that can help you learn some things to do with your child to help him hit milestones. Additionally, in Maryland there is the Judy Center which is a state mandated program for early childhood education.
http://www.parentsasteachers.org
http://www.judycenter.com/partners.cfm
We are currently working with a counselor from the Judy Center every other week and this is helping a great deal.
When my son started pre-school they tried to work with him but I got a letter asking us to remove him. I 'fought' back and went in to speak with the director because I didn't feel like they had been communicating the 'severity' of his behavior to me. He is still at that center and doing well. The Director asked me if she could call in someone from Parents as Teachers and that's where my journey started. our PAT person hooked us up with the Judy Center.
I would speak to the director of the pre-school. 3 years old sounds awfully young to be sent to the principal's office. His behavior (like my son's) requires different techniques to manage. If the teachers in your son's preschool are properly trained, they should have at least an idea of how to deal with his behavior. Being sent to the office isn't the answer.
Also, punishing him at home long after the incident is not going to help. I urge you to limit TV (same problem we had...) and definitely, contact your local Judy Center and Parents as Teachers. Involve the director at the pre-school also, tell him/her you want to have your son observed in the school setting by someone from the Judy Center (the preschool should have the number for the local Judy Center--if not, shame on them.) If you work as a team with the school, things can and will get better.
an added benefit is that the people at the Judy Center can and WILL suggest modifications to the center's programs, even arrangement of the furniture ect in the classrooms, to help the management of behavior. You may be surprised, the director may be reaching out to get your support and help because parent involvement is the most effective way to help not only your child but others indirectly.
You are NOT alone, I am also sure that your child is not the only one having behavior problems (there are only 25 kids in my son's center and there were at least 4 with similar issues).
good luck! and please let me know how it turns out!
B. M.
PS--I just saw that you are in VA--I found this website www.infantva.org (googled: "early childhood intervention virginia") I bet someone there could help you find the right resources in VA that is equivalent to the Judy Center in MD.