For the science courses, this is totally up to the student and family. Some students find they do best when they read the text first before a lesson. Others like to use the text to study while preparing for the module exam. This lets them skim over what they know well and slow down with material they are still mastering. 

If a student is enrolled in a discussion course, foreign language course, or a flipped course those do require the student to have done the reading or have done an interactive lesson prior to the class time. That is because they will be performing or showing what they learned in the class time. In a language class that would be to use the language learned in the lesson. Discussion classes it is so the student can engage in analysis on what they have read or learned. In flipped classes, there will be a group activity or project that will require the student to put what they have learned to work to solve an activity.