Interesting take on it. I go for the simpler, "You get what you pay for" adage. The reason that a majority of teachers aren't even close to approaching "exceptional" status truly is because of the salaries. Those with talent can make 2-3 times as much in the private sector as they can in the classroom. Many forego the extra pay and teach anyway, but they are the exception. The ones who fight for the positions are the ones who can't get that nice union pay scale, government employee benefits, and job security anywhere else. Those who have other options frequently leave when the going gets tough. Those who don't have other options, stay put. (The majority of teachers follow two paths: leave after 3-5 years or else stay for 15+ years.) This process inevitably finds the largest part of the talent pool leaving. The remainder could be easily said to be "paid more than they're worth", but it's the fault of the process, not the fault of those who are trying to maximize their opportunities.
Personally, I took a 5 figure pay cut to go into teaching, and later another 5 figure pay cut to teach (math) at a smaller, rural school. My SAT was close to 1500, my SAT Math was a perfect 800, my GPA was over 3.5, I had a bachelor's degree (with honors) before I went for the Education degree, my GRE was in the top quintile, my students class average standardized test scores have always been higher than the last time they were tested, they raised over $10,000 for charities in my 4 years (mostly Breast Cancer), and most recently, my LSAT was over 160... after 4 years of fighting incompetent administrators, vile union regulations, unconcerned parents, over-indulgent parents, uninvolved students, and my ego (making less than my age was never in my plans, LOL!), I'm now leaving for Law School in August. I fall directly into the "leaving after 3-5 years" group. I would consider myself talented, original, motivated, and competent, but I'm leaving for greener pastures.
One story certainly isn't a statistically significant sample, but my case certainly supports both of our hypotheses.
Your personal story only serves to reinforce one of the ways that I feel the system could be vastly improved. You took your Bachelor's degree BEFORE going into "education" so you would certainly fall outside the statistics of those who go straight from HS on to "education" degrees in teacher's colleges. I don't believe most folks have a problem actually paying the TEACHERS who are truly knowledgeable in their particular subjects for their talents. Where I, and most others that I talk to, have a problem is constantly having the "children" and "education" brought up every time some bureaucrat wants to raise taxes. You stated (and it is a known fact) that teachers in many private schools receive higher salaries (and justifiably so) than their public school counterparts. The differences lie in amounts and types of "education" and personal initiative on the parts of these private school teachers, IMHO. Also, it costs MUCH less to privately school a child than is spent on "public education" for one. The reason? The government run education monolith that is top-heavy and corrupt. I say again, if we could rid of the federal department of education AND its state-level counterparts, we could get back on the road to putting the money where it needs to be with funding and control entirely from local sources. The way I see it, this would solve both the teacher's and the parent's dilemas. The teachers could be individually compensated based on actual merit and the parents would once again have a say in what and how their children were learning.
BTW: Good luck with your latest educational endeavor!