It's different if the kid learns to do it him- or herself. The problem is the parents doing it.
Yes, aggressively nagging your way to the top works, unfortunately, because our systems are resource-starved and respect for authority has steadily diminished, as has the willingness to employ more competitive authority figures (e.g., low teacher pay). Creating firm, collaborative consequences for students who aren't doing the work and rewards that creatively encourage them to keep striving is tough. The MMM model basically says "don't worry about the public schools doing all the work - you'll do a lot at home," which is great for those that can, but not something we generally do enough. Enough students and parents are far more concerned with the results than the learning that result-fixing is its own job, in part because of the outrageous amount of testing kids are subjected to, which teachers also really hate. But teachers aren't in charge of it.
The notion that teachers control this is completely insane. Failing a student can get you yelled at, forced to change his grade, or even dismissed as you are blamed for your students' scores (as if they were completely uninvolved - in other words, not a collaborative process). Every nasty retail encounter you've ever witnessed? Imagine those people are parents who lobby for their utterly flawless children and you can guess how fun teaching is outside of the classroom, which is about half the time. Administrators overwhelmingly want those problem encounters to go away, and they incentivize teachers sweeping them under the rug by questioning them at review time if there are too many complaints, and there will be too many complaints if anyone is failing. Parents are strained by many single-parent or dual-working-parent households where folks are extremely critical of their schools (like, buying 500k houses "for the school system") but not being particularly demanding of their children (or too demanding).
I would have loved to be a teacher, except that I don't think we like teachers very much, even though we say we do, because we suspect maybe we should. But the attitude of even many college students when I was in college has increasingly become a paraphrasing of "I pay/my tax dollars pay your salary, so I deserve...". I'm still going to consider it when I'm FI, but between the pay and the administration directly opposed to your doing a good job, I think I'd have to not sweat losing my job to do it well.