I don't think you can overhaul the education system and retain rotting foundations. The very center of the academic mindset is such that it cannot help but produce a system where almost everyone fails. It doesn't matter if that happens under capitalism, socialism, feudalism, whatever.
One thing that stood out right away though is the worry about muh standardized testing. There is nothing wrong with a standardized test in of itself; tests fucking ought to be standardized, rather than subjectified so that special people get to take special tests. Subjective testing just leads to people being pre-assigned academic castes. The problem with the existing standardized tests is that they aren't very accurate or useful for determining ability. I don't know how the hell anyone thinks multiple choice tests are at all acceptable. Of course, the multiple choice tests are not really the core of educational policy - sure your official grade is based on the test, but your real grade is based on which academic caste you are assigned when you enter the school system. If you're an average student, as a rule you are not going to have a place in the future society, your role is to be someone fit to draft into the military or the low ranks of the civil service, or if your behavior is unacceptable / positions are not needed to be fuel for the base economy. Only the college-bound students, delineated at an early age and never much more than 20% of the population, are to have any future worth noting.
This 20% of the population possesses all of the machinery to conduct a revolution, and will never tolerate being in an inferior position or under the watch of the underclasses, even in a superficial way like being obligated to serve the people and maintain the government to a level where the underclasses can at least live a decent life. The only reason the underclass is not totally sacrificed for their body organs now, is because such a thing would be logistically impossible and economically problematic, and the underclass has the habit of not cooperating and scurrying around like rats when attacked. Hitler and the Nazis learned that and weren't as successful as they would like, and they openly disdained civil society and democracy in a culture that had little genuine history of democracy or liberalism at the time. The next time such a regime conducts a revolution, they are not going to let themselves bend to the small decency of ordinary people, and the behavior of the current generation is a perfect example of why most of us are fucked.
Anyway, I think you need to do more than adjust the education system to reflect idealistic reality. Shit doesn't work like that - schools, universities, churches, they don't build their education systems to do the right thing or idealism, they build schools to reinforce the existing social structure, or effect changes that suit their class needs, and the teachers within them have their antagonistic class interests with the administrators. The wants of the uneducated underclass do not matter, and never will. The Prussians knew exactly what they were doing when they built their model, and that model more or less informs the methods of education used today in the public school system. Universities are literally social clubs - you don't go to university to learn, you go to university to pass the credentialing process and make the connections necessary to join higher society. (That many people entering the university system fail is neither here nor there.)
If I were looking for somewhere to overhaul, I'd look at the universities. Since the universities have a large degree of independence (and how does no one question the independence of universities under capitalism, and how student loan debt is exempt from bankruptcy protection?), this is not likely to happen.
I don't really think you can question it, ultimately, without questioning the humanism that has underpinned the liberal enlightenment and the socialist movement; and then, you would also have to contend with the vast horde of reactionaries who explicitly want to restore monarchism and divine right, which is even worse (and ultimately, rooted in the same mystical superstition). I simply do not see a case where that happens, either if socialism prevails in the long run or, more likely, eugeno-fascism and an eternal dark age snuffs out any such thought forever. Humankind then will be a closed loop, like a masturbation addict that makes excuses and turns into a goddamn incel.
