Seems like if McD needs this sort of labour its a weird business model. It can only deliver by paying people supported by their parents who are doing the work for pocket money or experience. And can only work outside of school hours and will need to quit in a year or two.
Now if they pay the teenager half the wage the same adult is doing then someone is getting a raw deal.
Now if they pay the teenager half the wage the same adult is doing then someone is getting a raw deal.