That's fair. I took a class while getting my Masters that used Scheme (having learned Scheme on my own ahead of time) and, after getting past the parts I was already familiar with the language on, I found it really difficult to grasp what they were trying to teach me. I can't say it's what you experienced but I've tended to find that higher level education courses that utilize Scheme tend to operate on a level of abstraction that's hard to grasp unless you already know the big picture they're trying to impart.

Regardless, I hope it's easier the second time (if you ever do give it another try).