Hi Julie,
Absolutely! I am a 21-year veteran in the profession. I would not dear walk into a class without doing a problem, test, quiz, etc. As the instructor, you should no the unclear points (fix them) as well as challening portion of any assignment because you should have already done them. Although, I have know some intructors to go into class without having done problems, quizzes, tests, assignments, etc.
Patricia