Hello @martin_kabat
Thanks for posting this in the Canvas Community!
This is an interesting question that I really dug into. I was able to look at the Canvas permissions page HERE. The permission for Pages - update actually Allows the user to view page history and set front page. Keeping that in mind, it also Allows user to edit course pages. If you were to disable this for the teacher, they would no longer be able to edit the pages in their courses from my understanding.
I don't see that there is a way to separate the two permissions that this is responsible for. You "might" be able to do something with custom CSS for this to hide that option.
Hopefully this helps!
-Colton