How dare I say public school teachers are just in it for the paycheck?

What's wrong with just being in it for the paycheck?  I doubt my grandfather spent his childish nights dreaming of someday owning an Exxon station.  I doubt yours thought:  shipping manager at UPS!  They did those things for a paycheck.  And they were good, solid citizens who contributed a lot to their communities and their families.  (Well, I can't speak for your grandfather.  But I'm guessing.)

There are many fine teachers who have a real calling to teach.  But we can't build a school system that depends on everyone being a gifted natural teacher with a fire in the belly for imposing civilization on thirty godless savages every term.  We need a system that produces good results even when the teachers are just there to do a job.

Microsoft does not depend on every salesman being passionate about the XBox, every payroll clerk having dreamt from an early age about giving something back through the power of the healthcare deduction.  Institutions work because they create systems--situations--where the easiest thing for employees to do is to further the institution's goals.  These systems are more than a little imperfect.  But they work better than a system where employees can't get fired, get no reward for improvement, and have some aspect of every moment of their day scripted by a bureaucrat who isn't even in the building.  If we'd wanted our schools to do a poor job of educating students, we could hardly have hit upon a better model.