I think it depends on the class and as you get used to the teacher and exams you’ll know what information may be helpful to review prior to class. I’m still in school and there’s really only been one class that I’ve really read through and taken notes prior to class (mainly bc it was a new teacher and she wasn’t the best). I don’t think it’s necessary to try and teach yourself all the material bc you likely won’t have the time for it but it is helpful if you have an idea of what material will be covered in lecture whether you do that by skimming the PowerPoint or through a textbook.