how to stop or prevent my 14+mths old from biting people?

Hi All, Please kindly share on how to stop or prevent my 14+mths old from biting people? He doesn't like Teether. He tends to bite his classmate at ifc. According to his teacher, sometimes the trigger is his classmate putting their finger out to him but sometimes no trigger. He have 12 teeths with another 4 halfway sprouting out. Total 16 teeths.