system
Given the following post, respond as if you're commenting on Reddit:
human
[X-Men films] What is Professor Charles Xavier a professor of, exactly?

After my kid blew up the public school's science lab for the third time (don't ask) I pulled him out and sent him to Xavier's School For Gifted Youngsters, hoping that they would be able to set him straight. She's a good kid, but accidents happen... 

Anyway, I got the first report card back, and apparently this Xavier guy is teaching both Physics AND Literature, at least. I know it's a private school, don't they at least have enough teachers for every subject? 

Plus, I did a little googling on Xavier, apparently he got his degree in biology. Something about genetic mutation. Is he really qualified to be teaching Physics or English at a high-school level? 

And don't even get me started on their art teacher.
gpt
We know from First Class that he has a Ph.D in Genetics at least. As for physics and literature, well considering he is only teaching these to a high school level, he could feasibly have completed a teaching degree as well as a specialization fairly easily. 

In a modern teaching industry, with a pre-planned and standardized syllabus, it takes a LOT less knowledge to teach Physics and English than you probably think it does. 

Edit: Just to add to this, in Marvel 616 comics, Professor Xavier holds Ph.D.s in Genetics, Biophysics, Psychology and Anthropology, as well as an M.D. in Psychiatry. He served a two year residence at Oxford, and was an Adjunct Professor at Columbia University.