Homework is fucking important.
For example, doing an entire Maths A-Level, which usually takes two years, in a single year. We were going at a pretty rapid pace, because we needed to be, and were basically doing a topic every lesson.
The worst thing was, we did no classwork. Whatsoever. She also didn't ever collect in homework, so we never did it. Basically, we simply watched her go through the stuff without ever actually doing any of it ourselves first-hand.
Wasn't so bad as we were going through, but when the exams rolled around and we realised that what we knew amounted to a little more than absolutely nothing, things weren't fun. Took some hard work and revision to get the marks I wanted and needed.
Sure, you could say in the end everything worked out fine, but I don't think it's the best way to go about things. New teacher this year, again doing an entire A-Level in one year, but Further Maths this time, which technically should be harder. However, I've found it isn't, because this teacher gives us proper worksheets to do in class and for homework (he gives us shitloads of it too). As a result, I find I learn the topics as we cover them, and only need some light revision to remember stuff I've forgotten before the exam, rather than having to learn the entire syllabus for basically the first time in the space of a few weeks.
Maybe these sorts of things have to be learnt from personal experience, but lets face it, kids are lazy, and if you don't make them do the work, they won't. And I think it's harsh if their exam results suck simply because of that fact.