Students are no different then any other and they will rise to level of expectations you provide. about 20% of a class will do excellent work without much intervention from the instructor. About 60% will do what you expect them to do and will (like water in physics) go to the lowest energy point and due the minimum to get by if not encouraged by the instructor. About 20% will do the minimum or below the minimum no matter how much encouragement is provided. This means that effort to reach those who are willing to engage is critical. Off course each class has its own academic culture and the percentages are not fixed. David