A substitute teacher at a middle school in the St. Louis suburb of Normandy is facing charges for allegedly threatening a middle school student with a knife.

Authorities say 64-year-old Stanley Covington placed a knife against the chest of a student in a math class and threatened to stab him. Covington is jailed on $10,000 bond.

Normandy Police Chief Frank Mininni says it happened Wednesday. Covington told police that someone in the class threw a calculator that hit him in the head. Covington said he went to get a security guard and returned to find that a student had placed a knife on his desk to intimidate him.

But students told police that Covington pulled a knife and threatened to cut the student.