I think most of our seniors are not prepared for college. It becomes evident senior year because nowadays, that is the first year in which actual college level work is not only hoped for or expected, but required. I am not sure how to handle all of this, what to do about it, but I have realized that naming the feeling is important: frustration.
That is more useful than my default reaction, which is that I am not working hard enough to identify and then remedy the precise problems. People need middle school educations yet are in college, so a good professor would be discovering how to work middle and high school into college and have the students graduate school-ready in four years.
My program for not getting too depressed is to name how I feel in a way that is not terribly oppressive to me. “This is all my fault, we should only read short stories and one-act plays, what am I thinking?” is not really a useful tone to take even if it does turn out to be true that that is what we should do.
Axé.
coldhearted scientist وداد 
A few years ago I decided I was teaching high school to the undergrads and college to the grads. Resigning myself to that makes me happier, better able to focus on teaching what I can to those I can reach. Middle school would be even more discouraging, however.
Yes, I started the HS to undergrads and college to grads thing in the 90s, but the issue is middle school–the thing is that I do not have full skills to teach basic reading, there are things the elementary and middle school teachers knew about teaching that I don’t.