Biting and violence (ie hitting/scratching/etc) by preschoolers is usually related to the need for attention. I would be concerned that the teachers at your son's school may not be paying close enough attention to what the children are doing. Are they down at the child's level, actually playing with them instead of just standing up supervising? (Or worse, talking to each other!)
It sounds like your son has discovered that acting out gets him attention, although it is negative attention. Make a plan of action with his teachers. Say no firmly and give him a time-out. Then give lots of attention to the victim. If your son gets very little attention from biting, he will stop. Especially if he gets lots of extra praise and attention from his teachers when he is playing nicely and behaving appropriately. At home, do the same. Try to reinforce good behaviors, and role play what to do if someone take away a toy or does something we don't like. Sometimes preschoolers react a certain way because they have not been taught the right way to react. Good luck with your son. This may take time, but with patience he can overcome this.