Maybe, depending on the circumstances and the facts of the situation. I can think of many factual scenarios in which such conduct by the teacher would not be unlawful or even improper.
My responses to questions on Avvo are never intended as legal advice and must not be relied upon as legal advice. I give legal advice only in the course of an attorney-client relationship. Exchange of information through Avvo's Questions forum does not establish an attorney-client relationship with me. That relationship is established only by individual consultation and execution of a written agreement for legal services.