Three charecteristic of a good class.
If you ask most of the students what is the best thing makes class good for study, most of the time you will get similar answers. As a student I believe a class is good or bad it’s depends on instructor and student mutual relation of understanding, students respect to instructor and behaviour of students to instructor and instructor to students as well. If you ask me a question what makes a class good for me then i’ll say fun with study, friendly relation with instructor and in class activity which attracts to be in the class everyday.
Your beginning of the paragraph is kind of off topic, because you wrote about what is the best thing makes class good for study, not about three characteristics of a good class. However, general idea is well developed.