A.R.
Threatening to kick a child out after one day of biting incidents, with no history, seems a little extreme.
Can you spend a day in the class and see for yourself what is going on? There may be triggers the teacher isn't picking up on but you will.
Both my kids bit, and it had nothing to do with vocabulary - not only were they very vocal, they also knew how to sign. It was a frustration thing, they just reacted. My daughter bit once totally unprovoked, only to figure out later the child she bit had sat in her seat for the third time that day - she was ticked! Not an excuse, but an explanation the helped her teacher deal with it better. We also found it to be cyclical. My son would bite, then be bit and stop. After a while he would inevitably be bit again and would turn around and bite someone else within days.
My kids finally kicked the biting habit when they attended a daycare with a 'shadowing' policy. Kids who bite more than once in a day must be within arms reach of the teacher for the remainder of the day. If the behavior continues, the 'shadowing' duration increases. Didn't take more than two sessions of shadowing for my kiddos to stop biting, they hated losing their freedom!
Good luck, and remember it is a very common phase he will grow out of.