I don't want to go too hard on teachers. A lot of them are probably highly skilled, well meaning people. Sometimes, when I make this argument I lose some nuance in my bombast, and it would be unfair for me to make this solely about teachers. And you're right, many kids are failed by their parents when it comes to learning out of school - I don't want to overlook that point.
But, if schools can spend this much money, and still fail this many students, is it really worth it? What if parents could take that 14k and instead pay a private school? Wouldn't that be better?
Perhaps the system itself is flawed. Perhaps, as you point out, students need smaller classes and more personal attention. Public schools are factories, not artisan workshops.
It does say that we are pouring a massive amount of money into a hole and getting poor results.