The leftists in this thread? Indeed.
No. The South Dakota state legislature.
Why, what did they do?
In all seriousness, though, because the rate of both school shootings and violent teacher-student attacks is close to nil (I think more have suffered from the former than the latter, but it may just be that isolated incidences of the latter go unreported), it's doubtful this'll have any effect; it's just a feel-good measure so the denizens of the South Dakota legislature can be reelected.
Ask anyone who has taught whether he wants a loaded gun of any kind in a classroom -- even if the teacher has the gun. Maybe the ordinary school teacher will have more common sense than state legislators. Maybe voters will think before they vote next time.