There were signs in the sky, but I did not know
If one more student tries to tell me that Constantine was responsible for making Christianity the official state religion of the Roman Empire, I'm going to stab them with a Chi-Ro.
(I agreed to help grade papers for a friend with a classful of undergraduates. I despair of humanity.)
(I agreed to help grade papers for a friend with a classful of undergraduates. I despair of humanity.)

no subject
Not so much worse than stabbing them with a cross-hilt sword,* I should think, but if it would make you feel better you could strike them with a Thor's hammer instead--not as symbolic, maybe, but appropriate.
*If you were Catholic I'd advise you to find a Jesuit historian for when you went to Confession afterwards. I'm sure he'd be understanding and let you off with no more than a couple of Hail Marys.