If they truly believe they can do much better babysitting, then my answer to them would be... what the hell are you doing teaching, run and get a babysitter’s job!!
I think that would shut them up, because they know very well that there’s no way they could make that type of money babysitting - their little sophomoric exercise totally neglects the economy of scale.
It would be like someone calculating the cost of building a single pencil. It would cost you a fortune - cut the tree, machine it, mine the coal, get the rubber for the eraser, assemble it... However, with economy of scale, you can buy a pencil for 10 cents.
Regarding the numbers themselves, what it costs the parents to send the kids to school is not just the cost of the teacher’s salaries, it’s the cost of everything else - benefits, administration, supplies, support staff, etc. The total cost per pupil is over $10K, which comes to $300K per classroom, not $50K. And that does not include building costs.
Lastly, and most important, what the “right” or ‘fair” salary should be is not determined arbitrarily or comparing apples with oranges. It should be determined by the marketplace, and the unions absolutely refuse to allow that. Why? Because they would rather have a monopoly. It’s good to be king! (or union boss). As a result the good teachers get penalized. They would most likely be making a lot more in a private school system.
Don’t forget the permits for the lead. Without that it nothing more than scratching the surface.