Thank you, you have very eloquently conveyed exactly my concerns that people may not be able to re-train for a new type of job when their old one is automated. Sure new school leavers may be qualified to supervise and manage the machines and therefore balance the employment figures but the old workers won't just vanish into thin air, they will be the ones left on the scrap heap.
While it's not an exact comparison, I think a good real world example is the closure of various British heavy industries in the '80s. Most of the workers in those industries were unskilled and when the coal mine/steel mill/factory closed there weren't any new jobs in the area that they were qualified for and they weren't able to re-train for anything else. I could see automation doing exactly the same thing.