It is a routine that has been learned in class. It's not the function of the teacher to get the students to settle down every morning. The students know the procedure and go about their jobs without anyone's telling them what to do . Achievement is the result of academic learning time. If students know what they are to learn, you increase the chances that the students will learn.
Ineffective assignments tell students what to do.
Do the problems on page 35. Effective assignments are structured with objectives for students to demonstrate competence. You tell a student what you want accomplished. Then you give them procedures for what you want accomplished. Use checklists, rubrics, etc.