A minor under 16 years shall not be employed in an occupation subject to this act for more than 6 days in 1 week, nor for a period longer than a weekly average of 8 hours per day or 48 hours in 1 week, nor more than 10 hours in 1 day. The minor shall not be employed between the hours of 9 p.m. and 7 a.m. A minor who is a student in school shall not be employed more than a combined school and work week of 48 hours during the period when school is in session.