First, the lessons are too hard. Sometime it is harder than the students’ level. These make students cannot understand or they may question why they have to learn these difficult schoolwork. The students will lose their motivation to do homework and review their lesson. Another cause comes from teachers. They do not know how to explain the hard lesson to the students. Some teachers give much homework instead of teaching, since they think these assignments will help students to understand the lesson clearly. But that is not true at all. Students who have been confused cannot do that homework. They will copy schoolwork from others or let someone do it for them. The result is they cannot do the examination and get bad grades.