I can agree to this, except, lets do it this way: lets leave the minimum wage where it is for teens, and raise it for everyone else. That'd also solve the problem of adults working jobs that are meant for teens.
It wouldn't be such a big deal to prevent adults from taking these jobs, it just needs to be more attractive for companies to give them to students. So, the lower wage alone would be a good enough incentive for them.
Once the minimum wage was lower for "school jobs" the market would efficiently define which jobs can be given to school kids and which can't.
1) Increased unemployment in the adult segment, due to teenagers stealing their jobs.
2) Need for government agency to enforce the age requirements. Modeled after immigration authority, such agency would need to be able to raid the businesses in order to do age verification, to ensure that teenager-compatible jobs are not given to adults. Also, such agency needs to ensure that people are fired on the day they reach 20th birthday, and thus lose the "teen" status.
If they have not received raises after spending many years with the business, then it's unlikely that their years of experience matter.
And if their years of experience do not matter, they would be replaced with lower-cost younger labor well in advance of them reaching particular age group considered "older".
I can agree to this, except, lets do it this way: lets leave the minimum wage where it is for teens, and raise it for everyone else. That'd also solve the problem of adults working jobs that are meant for teens.