I have to agree with the professor on studying math, but I have to say that it is very strongly subject specific. With a subject that builds on itself like math or any language, you really cannot cram a significant chunk in at midnight before your test. So study a little through the term and get your sleep. However with subjects based on large numbers of facts, such as biology, you most definitely can cram and should.

Therefore while I agree that cramming won't help in math, it certainly will help in a lot of subjects.