The solution is simple: separation of school and state. If parents had to pay for education they would naturally want their kids to work at learning. ‘Free Stuff’ is naturally going to be treated with contempt.
No, the best solution is to have the ‘big’ exam at the end of the 8th grade. If that kid isn’t capable of high school work...stop his path there, and send to a craftsman shop that requires just 6th-grade reading skills and apprentice-train the kid from that point on. If he doesn’t show up or show any attention...drop him off at the state unemployment office for placement at Burger King/McDonalds at the age of fourteen. You don’t need to waste time or money on the kid.
That does not deal with the real problem. Lower intelligence of the parent{s} is a major reason these kids fail. Those in the lower IQ levels don’t come from the class which can pay for private education. They are the majority of drop-outs, low income and imprisoned.
It is a much more far-reaching problem than just having public schools teaching crap. The culture of at least 30% of the population must change. And you can add the academics to that number.