I work at the Joint Special Operations University, when we see the class list we break the students out into groups. We seperate them from branch of service and origin of country. When put into working groups, they tend to break their shell so to speak and start participating more as they all have different areas to draw from with their back ground and experience. Then on day 3 when then are all set, we'd change their seating assisgments after they left for the day and make them sit somewhere else in the class on day 4. They never know what is coming next. Keep them guessing and they will respond/participate.