As to the bad management...I think it goes hand-in-hand with the lack of workers. People who cannot find their bidet with both hands are in charge because they need someone and got what they could for the salary they were paying.
Have your son write a nice worded letter to the corporate office detailing the problems and why he left. It may not solve the short term problem, but at least they will know why they are losing good people...I've heard that most people quit their manager, not their job.
As to the bad management, the best way I could put it to my son not to get angry at his manager is because he's dealing with a middle aged man driving 30 minutes to drive to the same place he was hired as an assistant manger because he (my son) only lives 7 minutes away from the store and apparently this manager thought he would make a good "assistant".
I never try to "poo poo" someones position in work, because when I was younger, I've held a lot of "poo poo" positions.
When I was in high school, went to the movies with a good friend and his father. What I remember is the guy at the concession stand was horrible to deal with, and my friends dad telling him that if he can't give 100% at work and love what you do, find another job that you love and will give 100%.
Thought about the letter to management at dollar tree, but at the end of the day, my son loves the car wash (his other job he's been at for some time), gets along great with his manager, and is happy to work 7 days a week when school get's out for $12 vs the assistant managers job at $12.50 an hour for two days work.
I told my son he is blessed. He wants to work because he wants to make money. At this point in his life, he doesn't need to work as hard as he does, but he actually wants to (we're prefer 20 hours a week when in high school, but he has pushed 50 hours during last summer out of school). End of the day, he's a good kid who listens, and my wife and I have to remind ourselves that when you're arguing with your 18 year old high school senior, we could have more issues than arguing about cutting back his working hours.
I feel sorry for the one girl at the dollar tree he worked with. She offered to do the work schedule for the manager, but he refused to let her do it. She's stuck there because she HAS to have the job. Good girl. Remember meeting her when I started this thread.
When in management IMO the whole idea is to surround yourself with better people than you. That said, I guess some people are afraid they'll lose their job to someone better than themselves. Who knows...
And for the record, a VERY long time ago, I was a manager,
NOT an assistant manger of a convenience store

Even back then, you were just happy to have people who actually would come to work when they were scheduled for work and just doing what they were told.
I'm was just kind of ranting over the situation because I'm scratching my head over it and it sounds like very stupid management at best.