"It just didn't matter as much. There were ample good jobs in manufacturing and agriculture and other manual trades which required only a marginal high school education, or even less."
Agreed. We need a strong system of apprenticeships in labor-intensive jobs for these kids. Switzerland has this system and it works great.
But we don't want a system for this created by gov't, either, it should be created by private industry. Problem is, unless it's something that the kids get school credit for the school administrators will scream because they lose money if those kids are pulled out of school early.
Personally I'm all for abolishing public schools entirely, and replacing them with a voucher system in the amount currently being spent on public school students. Make the vouchers redeemable by anyone, including homeschooling parents and private tutors, who the child's parents register as the child's educator in advance, and who can get the child to pass basic verbal and math tests, with passing score set at the 50th percentile of current public school averages. Pay AFTER the child passes the test (which must be administered in a different location from where the child regularly studies, and by people who have no financial interest whatsoever in who passes or how many pass. At the very least, this would raise the achievement level of 50% of the students currently in public school at no additional cost to taxpayers. Keep in mned that when capital expenditures (i.e. buildings, land) are included, most school systems are spending between $10,000 and $20,000 per year per child (with $10,000 being mostly in rural areas where land is cheap and teachers can be hired for less and students don't expect Olympic swimming pools, etc.).