Students spend up to 8 hours in school each day. By the time students get out of school, they either have to complete another hour or so of homework or have several extracurricular activities that limit the amount of hours left in their day.
By limiting the normal, 8 hour school day, it will now be cut back to 5. Schools in each district can settle what time the day starts and finishes, but the school session should be no longer than 5 hours per day.
Also, students have a mandatory 180 day school year and limiting the amount of school hours will be a less vigorious educational schedule. It will give the students time to complete extracurricular activites and put more effort into school work.