One problem I keep running into in the classroom is my students' vague sense of history.
In a way, they're not at fault. There is no history prerequisite for my class, and high school history tends to focus on wars and various dudes seizing power rather than the way people lived, worked, ate, or amused themselves.
On the other hand, when my students this semester wrote a paper on "Cinderella," which specifically marks its historical vagueness with "once upon a time" (or in the translation they used, "once"), over half of them wanted to refer to a "back then" with no there there. Back Then, women had to get married. Back Then, beauty was really important (unlike, apparently, Today). Back Then, the prince had lots of power.
A fairy tale makes itself historically indeterminate: "il était une fois." But because of my students' lack of historical background, the performed indeterminacy of the story was not distinguishable from their own fuzzy grasp of history.
I'm working on ways to counter this. Of course I gave a spiel about the "Since the dawn of time" introductory paragraph and its Badness. Also, my students often use "back then" and "at the time" as markers of historical distance. I am trying to replace these terms with more specific markers, like "among servants in mid-eighteenth-century Britain." Finally, I try to give historical context to the things we read in class.
But it's an uphill battle, when they've been trained in presentism for years. I wonder if there's any pedagogical literature out there on bringing a historical mindset to the classroom.