IF the average school, whether you like it or hate it, dropped grades and left everything else the same, the public education would still be unsatisfactory. It's unsatisfactory for reasons having little to do with grades.
What is unsatisfactory?
1. One of the unstated functions of education is to keep children, youth, and young adults off the streets. To many youth on the streets, especially the wrong kind of youth (varies from place to place) makes some adults, business people, and police nervous. As a function of keeping children off the streets, schools also help regulate the labor pool, keeping younger adults in consuming rules rather than producing roles. (Of course, educational programs -- even state operated and private universities and trade schools -- are a form of service production which needs students in class.)
2. Schools are instruments of ideology for the ruling class (whatever ruling class you have got). History, civics, literature, social studies, and sometimes other subjects as well, are tailored to fit the ruling ideology. So, for instance, you won't find labor lauded and honored in history books; you won't find Manifest Destiny (an American obsession) described as aboriginal genocide. You will find the super rich of the the 19th century described as robber barons, but you won't find the current superrich described that way.
Eastern Europe is going to have it's own ruling ideologies to deal with in school.
3. The standards to which American students are expected to perform are generally too low. About 10% of American students receive a very good education -- high standards, good teachers, good curricula. Another 10% to 20% get a reasonably good education. But maybe 70% get a sloppy, low-grade education. It isn't what students want, necessarily, it isn't what teachers want either, but at least in this country, many people are at a loss to specify what children really need to learn.
4. The capitalist class aggravates the whole problem of education by structuring the economy to render many kinds of workers irrelevant. Lower skilled workers are obviously less relevant to the American and Western European economies these days (because we exported all that work to Asia). But so are some skilled and professional fields becoming irrelevant. Just how necessary is an old fashioned literature major (like myself, though I graduated from college 50 years ago and am not looking for work anymore)? No very.
How necessary are the many people who used to, and still do, work in middle management? Companies are laying these people off all the time and replacing them with computerized functions.
5. What is life for? Education should prepare people to answer that question, and then conduct their lives in the most suitable way to achieve at least some satisfaction and happiness in life. I don't think a lot of leaders have a clue, at this point, how to educate people that way. (Because, for one thing, to frankly address the problem of what your life is for, we have to admit to students that maybe their lives are functionally irrelevant.)