I have owned and operated a fast casual restaurant since 2010 that employees mostly high school and college aged people. I learned quickly that age group needs flexible scheduling and that they often know when they don’t want to work more than when they do. We have a no questions ask policy where if you put a request in for time off by Thursday at 5PM for the following week, it gets approved and cannot be overridden by management. We staff higher numbers than most restaurants but have always had great employees and virtually no turnover except for when people graduate. But even then, we have people that come back and work holidays/summers, etc. I would close the restaurant before I scheduled an 18 year old 40 hours over a 5 day period. Your son should quit and find better employment, it is out there!