I used to think so too, but I changed my view after seeing how high schools work here in the bay area. The schools here are super demanding, and students work crazy hours. It looks to me that the US schools are great for top students: demanding projects, strict disciplines, wide selection of extracurricular activities, abundant resources like AP courses and college programs, access to world-famous labs, professors and engineers, well-designed co-op programs with top companies, and of course, tiger parents who demand high achievements. On the other hand, we had public schools in Baltimore whose median GPA is below 0.5 out of 4. A stark contrast of two worlds.
That why it pains me to see that progressives thought that lowering standards would help students in need. The three years of Covid showed exactly the opposite.
I'm not sure how we can measure the number of students with discipline. GPA isn't a good measure as some kids may get As easily while a less gifted but dedicated student might get a B. Even measuring advanced placement isn't great since not all places have that tract and you still miss those less gifted but dedicated students. Plus, we seem to have a lot of grade inflation over the past 50+ years, which could mean it's easier.
There are certainly some students who are really disciplined/dedicated about their school work, but I would guess the number is less than 15%.
I did pretty well in school, but likely could have done better if I were really disciplined about school work. I usually rushed through homework and spent just a reasonable amount of time on projects. I'd rather be playing video games or sports, or hanging out with friends. I'd put extra work in on stuff I was interested in and probably learned just as much outside the classroom as in. Even stuff like school band I would rarely practice and still do well (sort of forced into it because the school would give busy work to the non-band members during the occasional practices during school hours). I went to a private school and participated in advance classes, and I still think 15% is about the number of students who studied hard and the rest of us could either do it easily or some would cheat.
That why it pains me to see that progressives thought that lowering standards would help students in need. The three years of Covid showed exactly the opposite.