"I’m surprised you still have a full set of teeth because if you lived at my house you wouldn’t have any teeth left" would this be a theart when said to my child by a teacher during a discipline action?
It MIGHT not be considered a threat because of the way she said it "if you lived in my house". However, this is language that the school board might find unacceptable and subject to discipline. Contact the principal to launch a complaint. If the principal does nothing, contact the superintendent.