That's one problem right there. Teachers should have a problem with the curricula these days, because much of it isn't designed to teach basic knowledge and understanding, and the results, by and large, prove that point to be true.
Most people did not go to school or went to one that is much different at the time of the founding of this country.
I thought your original point was that educational failures were not the fault of teachers, but rather some problems or other at home. Since many children were taught at home during the 17th and 18th centuries, and most homeschooled children today don't have these educational failures that we see in public schools today, what's your point?
The teachers I know do have a problem with the curriculum. As I said in another post, "It's the Politicians".
We no longer have spare the rod spoil the child we have touch the child and wait for the lawsuit. Public schools don't have any choice in which kids they have to teach. They have to take them as they come. We don't hear about the failures of home schooling as there are no standards and no reporting that I know of.
Some educational failures are the fault of teachers as many deaths can be blamed on doctors, planes crash because of pilots, and so on and so on. For example if Preachers were paid by their success rate on convincing people that abortion was wrong then we would most likely have to change their name to paupers.
I don't think that you can compare the 17th. and 18th. with the 20th. and 21st. century. This is like comparing apples to oranges. If you could read the Bible back then you were considered educated.