Today in my english class, we watched The Crucible. It had nudity in it, but I didn’t know that the video would show it until it was too late. Although I looked away at first, I looked back for a moment (out of curiousity or lust - I’m not sure). Was this a mortal sin?
I doubt it. But this is a question best raised with your confessor, so he can help you develop your conscience.
A teacher should always preview movies to determine if any objectionable content is present. If any such content is present they should let their students know of it. This decision should be based not on only the teachers morays, but based on those of their students.
Seeing how this teacher has demonstrated a lack of consideration at best or deliberate depravity at worst (you will be the best judge of that) I would suggest always checking a reliable Catholic movie review service before watching any future movies shown in this teacher’s classroom.
I checked one movie review website about The Crucible. It was rated A-III. This rating is for adults.
One last thought would be to pray for the teacher to be more thoughtful in the future.
Let’s review the three criteria of a mortal sin:
You didn’t know that the film had nudity and hence you did not have full knowledge. Also, you were not watching the film with the intent of indulging in anything pornographic. So I think you’re pretty safe, but it never hurts to pray if watching those things lead you into a near occasion of sin.