When I applied for a MLIS program, the school listed topics they wanted me to address in the SOP. These were listed at the end of the online app process, so I had actually written a rough draft of my SOP before I even saw them. If I remember correctly, the topics included what skills or attributes I would bring to the profession, what I expected from the SLIS, and what I felt the role of a librarian or school media specialist was, and what relevant work experience I could claim. They did not ask me to discuss specific classes or professors.
In general, I'd recommend that you personalize your SOP as much as possible. They would like to get to know you as a person and understand what drives you toward this specific career. I found a web page with advice on writing SOP's that I found really useful. It even uses a MLIS SOP as one of its example. Hopefully it'll help you too.
http://www.uni.edu/~gotera/gradapp/stmtpurpose.htm
Good luck.