I had a professor who taught algebra and pedagogy of math in local university. He has a nice scheme for grades (1 to 5 in Russia are F to A respectively): each lecture except the first starts with 3-5 minute test on previous topics, marks for working at practice hours and final exam. The grade was calculated as an average of avg(tests)+avg(practice)+exam, so you have to work throughout the whole semester or you won't have a chance for C or higher which is a minimum to pass.