I guarantee 75% of your students got lost along the way at some point, and — having lost the train of reasoning — are simply waiting for the class to be over so

I guarantee 75% of your students got lost along the way at some point, and — having lost the train of reasoning — are simply waiting for the class to be over so they can review the textbook and try to make sense of the subject matter. At least for difficult classes like physics and mathematics, which require uninterrupted thought and reflection to achieve understanding.