UMDNJ has a pretty full schedule but the only classes that are mandatory (i.e. daily quizes or sign in sheets) are OMM, Genetics, and Patient Dynamics that I can think of. Small groups and Case Based Sessions are always mandatory too. I pick and choose my classes for the most part so I go to maybe a half day of classes. Some people go to them all and some go to only the "mandatory" ones. It is up to you to decide how you will best learn, this is grad school and we are all adults.
PS We also have all the classes' audio and notes on the web, and for most classes the professor's powerpoints. So missing class and studying on your own is a good way to go sometimes.