This way it sticks in your mind. I feel more comfortable in a small group. From the other people talking, I get a better understanding than what I get in the lecture. The other students put it into better words. It helps to identify the main points.
Students are reluctant to talk in class to the professor.
Professors often make the deadly assumption that silence by students means that everything is fine. We conducted a research study at UMKC by asking our SI leaders to record the number of questions asked by students in class for a period of two weeks. On average, three questions were asked each week in each class. Of the three questions, only one asked for deeper insight of the course material. The other two questions generally dealt with mechanical issues such as when the next exam would occur.