When I as an academic I used to run extra classes at lunch time for the keen students covering topics that I thought the students needed to learn about, but for

When I as an academic I used to run extra classes at lunch time for the keen students covering topics that I thought the students needed to learn about, but for which we didn't have time in class. Theses topics were not covered in the exam so only those students interested in learning came. As for those students that don't have the prerequistes or the motivation to do the work to catch up, you fail as many as the university will allow and then scale up the class mark so the rest pass. At my university I couldn't fail more than 3% or 4%, but in some classes more than half really failed.