As with many things in life, preparation is crucial to language learning. Sure, you can attend your classes and go through your language software lessons without doing any work beforehand. Do note that you’re seriously shortchanging yourself if you go that route.
Remember homework in school? That’s what preparation is. If you do your assignment, you’ll be ready for the next day’s lessons. Same with language learning. If you do sufficient prep work, the chances of drawing the most out of your lessons proportionately increase.
Lessons fill you with information. That’s all it does. Everything else, you end up doing for yourself. Just like attending an entire semester of PHP programming won’t guarantee you can actually acquire the skills to write a MySpace clone, finishing a language course doesn’t mean you’ll pick up everything that was taught. Put simply, if you don’t do work beyond following the lectures, you aren’t likely to get very far.
If your language lessons ask you to do exercises, listen to materials or perform some field work, don’t dismiss the instructions as unnecessary. More than likely, those are intended to improve how you absorb the lessons, allowing you to gain much more than what you’ll end up with simply going through the motions.