I hate to say it, but an adult having sex with 15-16 years old teenagers does not make one a pedophile, the age of consent in most countries is 15, including China. Therefore what he did was not illegal, but still morally questionable, because having sex with your students is a disgusting behavior regardless. Anything below 15 however, would have labelled him as a pedophile in the eyes of the law. In a teacher-student relationship, one should remain professional at any given time, same as a boss-employee relationship.