No need for you to get involved or apologize for them. They are your class-mates and you should'n't make a problem for yourself. I have heard that this behavior is not uncommon in your class when they have a new teacher. I will speak with supervisor at the faculty to find a solution. In the meantime, whoever doesn't do the work or come to class will simply not be permitted to write exams or they will simply fail. I would like to help everyone, but I can't do it if they are not interested in even trying. But, not your problem, so make sure you study so that you can progress and get good grades.