What is the ruling on advising students who engage in acts resembling sodomy, and am I obligated to inform the counselor or principal about this, given my fear of being subjected to assault?

Denouncing evil is obligatory according to one's capacity, and the least of it is denouncing it with the heart, which necessitates leaving the place where the evil is committed. You can inform the administration or one of the trustworthy teachers to take the necessary action, requesting that your identity not be revealed. We advise you to associate with good people and utilize school activity clubs to invite to Allah.