No Bengali in BTech classes

Yesterday when I and my roommates were chit-chatting, one of my roommates is an assistant professor in CSE in one of the very famous (but small in size) BTech colleges in Kolkata. His HOD conveyed to him and his colleagues that the Principal became aware that some teachers teach in Bengali in the CSE Dept. They were warned by "No Bengali in Classroom". I, myself belong to the IT field and English is the only language that I've heard throughout the day but confused if it is the right thing to do for a college or not. The problem arose because of some non-Bengali students who complained to the Principal about this. What's your opinion on this?