For the Evulz? Not on their watch.
Unlike a Sadist Teacher, the Stern Teacher is always "tough but fair": a person who's got high expectations but is ultimately a Reasonable Authority Figure. The students might not be too fond of them personally, but they always respect them in the end and often achieve the best results in education (which does make it Truth in Television).
While cold and aloof at first glance, a stern teacher truly loves and cares for their students deep beneath and genuinely wants them to succeed in the best way possible at life. Constructive Criticism is their stock in trade.
Teachers of this type are firm believers of You Are Better Than You Think You Are, but, befitting their just-yet-harsh nature, they will always use the more firm version of the aforementioned trope. Then again, they're likely to be a Fun-Hating Confiscating Adult; woe betide the Class Clown who tries to get away with goofing off in their classroom.
They'll often be on good terms with the Cool Teacher. The opposing teacher types will usually butt heads over their vastly differing philosophies (whomever is proven right depends on the work, if there's a right answer at all) but there's often a mutual appreciation between the two in understanding that the other cares deeply for their students. On the other hand, they're often a Foil to the Enthusiastic Newbie Teacher, who they will see as a hopeless Wide-Eyed Idealist and who may see them as The Killjoy. (The Newbie will probably earn their respect eventually, but only once they've proven they actually are serious about education.)
Expect them to strongly disapprove of the lack of professionalism or care displayed by the Apathetic Teacher, and to be staunchly opposed to the behavior of the Sadist Teacher and Evil Teacher. Opposition to the latter two in particular often acts as an Establishing Character Moment demonstrating that this teacher really does care about their students.
Interestingly, in cases where a good teacher is forced by circumstances to teach their own child or other younger relative, they will adopt this persona to a greater degree with their relative than with the other kids, as an (over) reaction to the Embarrassing Relative Teacher stereotype.
Dmitry Vladimirovich Beklemishev, a near-legendary figure at MIPT (roughly, the Russian equivalent of MIT) once said in an interview that he tried many personas on during his long teaching career and found this one to be the most effective for the purpose of doing a superb job.
Sergeant Rock is the military version of this. Compare also with Tough Love. This kind of teacher is likely to have a Teacher's Unfavorite Student.
Stern Teacher has been suggested to play 3 roles. Click below to see other actors suggested for each role, and vote for who you think would play the role best.