I find Zinn an excellent source to get at point of view. I don't care too much for his heavy handed style, but he is effective at telling a history from below. It is good to get kids to see that all history is biased and not to take everything an author writes without questioning. If the teacher is saying that Zinn is always correct then that is a problem.
Here is the course page: http://apcentral.collegeboard.com/apc/public/courses/teachers_corner/3501.html