As far as bullying around, telling a grown up is right, but do not ask the grown-up to intervene. I was the target of a lot of bullying in my younger days. I grew up in the cities and kids were cruel. Once they saw that I had "real guts" they left me alone. Some became my best friends. Solution was for me: LOOK THE ENEMY STRAIGHT IN THE EYE when they are slamming you. Answer them back with things like "JUST TRY IT" or "I am not afraid of you" This rule I found to be true for me when I was getting slammed. I was scared when I said it but I stuck to my guns. I even had a pajama party and invited 2 of the bullies and a couple of cool people. That really works.
BUT, if there is any malicious behaviors on their part (sexual, obscene, rape) you MUST go to a grown-up you trust and ask them for help. They should know where to go (police, teacher and they should take you to the police, teacher).
I think you should tell the teacher too. but i don't think that will solve anything, the teacher might move the student to another seat. But you can try your best to ignore him and keep focusing on your work... if it continues the teacher might write him/her up.. !
I had this same problem as a child. Your smart to reach out and try to get help. The way you handle it will forever affect your life. Speak to your teacher privately or go to your schools guidance counselor. Ask to have your seat moved. If you are in middle school or high school, see if it's possible to be moved to another class. Most schools have an anti bullying policy. In the mean time, I've found being overly nice to people who are mean and mean spirited really drives them crazy. The bible says when you are nice to your enemy's it's like putting salt in a wound. Something like that. Remember, these kids that are being mean, don't like themselves very much so when they are mean to you, they feel better about themselves. If you need any suggestions of what to say, let me know. I'm so sorry your going through this.