A teacher in Aroostook county is being credited with preventing a knife assault on Tuesday.Officers responded to a call at Houlton Regional High School early in the afternoon. They say an altercation between two 15-year-old students began with a verbal exchange and ended with a female student charging at a male student with a knife. We’re told the teacher, Timothy Tweedie, saw what was happening and put himself in harm’s way to separate the two. Police say another teacher, Robert Kinens, heard the commotion and helped Tweedie restrain the student with the knife.Police say principal Marty Bouchard then talked the student into dropping the knife. Tweedie suffered bite marks to his hand but is otherwise unharmed.Police say the student’s father took her to the hospital for a psychological evaluation.Charges are expected.