[something123]

I think an OS class isn't meant to prepare you for working on the operating system. The vast majority of people that take an OS class aren't going to work on OSs, but they should appreciate how everything works. Using a language optimized for communicating "how everything works" clearly should be a priority!

[argonaut]

Yes, and that language is C. C is a very simple language, and it's very clear. If you're writing anything that interfaces directly with the OS, you'll need to know C.