It can be a great deal.
Science is all about asking questions and then going about trying to find the answers.
This means results can be unpredictable, inconclusive, and always lead to more questions. Now, don't get me wrong. These provide students with the skills to do science. In these controlled situations, specific concepts can be demonstrated. However, students must be given the opportunity to investigate and experiment on their own terms to fully internalize the information presented in class.