I'm planning to design my son's room to look like a prison cell.
Don't you think that is cruel? Does he deserve to have a room that looks like a prison cell?
Yes, he does. He received an F in class that was not his fault
Even if he got a bad grade you shouldn't decorate his room to look like a prison. It will lower his self-esteem. You should be more caring and encourage him to go to tutoring instead.
He is still a child and I think this will teach him a lesson.
You may feel that way but these types of punishment's rarely work and often encourage worse behavior. If you want your son to do better in school you should work with him and find him a tutor, and instill confidence in him that he can do better. If you treat him like a criminal, odds are he will become a criminal.