The curriculum includes a certain number of hours to study subjects. For example, 24 hours per week. You can learn 5 days-5 lessons – 6 days and 4 lessons. Apparently, for 5 lessons, the students get tired, and so they were transferred to 6-days a week. When I was in high school, on Saturday conducted the lessons for the Laggards. And the standouts on Saturday were a legal holiday. Maybe now the case.