Everyone deserves to be paid in accordance with the work they do. No one should be paid less than enough to live on, pro rata, depending on age and circumstances. 'Pro rata', because there are those who would work as few hours as they could get away with; hence the 'per hour' restriction. 'Age and circumstances', because most school leavers live in the family home, with one or more parents.
The aim is fairness and respect across the board.