If assignments are given weekly, another assignment has already been completed, and a third has been given. Student interest in the assignment from Class one may wane. Interval Students do assignment. Students send assignment to teacher. Teacher reads assignment and provides written feedback to student.
Teacher returns assignment Students read teacher's feedback.
The teacher can plan for class 2 having already had two-way communication with students about class 1. The students have received feedback from class one's assignment before class two begins. At first glance, this looks like a lot of work. Indeed, if this kind of cycle is used in a class that would otherwise have no written homework, it is a lot more work for everyone involved. But if this cycle is used to replace a cycle of weekly homework on paper, it's no more work at all.