All good points, but remember before the "public school" and college degreed teachers or even church academies from the middle ages forward, people still learned and became artists, doctors, lawyers, musicians, etc. It was through apprenticeship, working with parents and grandparents, learning from village elders, monasteries, traveling artisans, etc. And we still have that opportunity today.
And it is a well kept secret that teachers are not underpaid--that they do indeed have "wage justice." The Bureau of Labor Statistics figure a middle school teacher's hourly wage at about $57 an hour, higher than accountants or architects, and that was in 2011--probably higher now.