For once I wish the teacher just recognized that he had an unskilled but very fast and strong student and just worked from there. But let us see if the MC actually gets to learn something.
With the way his magic has been progressing, he might transport them home by forming rollers underneath them or something. He's got a lot of options going forward.
Isekai Mc's from earth that go along with slavery or morally dubious stuff when they legitimately know better. The paper-thin excuses for that kind of behavior just sour me on characters so fast.
Think I'll wait to judge the parents if he ever confronts them about it and actually communicates to them his feelings about this issue. Otherwise, we have no idea if he's just making an assumption.