We have tools to dynamically adjust curriculum difficulty for students who value education, whether because they're self-motivated or because their parents make them. The challenge is what to do about the large number of students - at many schools the majority - who don't. When you where dynamically adjust to a student who doesn't particularly care to study, or doesn't have the support to do it properly, you end up with the recurrent scandals where a high school is found to be graduating people who can't read.

Extracurricular studies are always possible for the students who are furthest ahead of the curve, and good schools usually do accommodate that. For the rest, I would argue that a fixed number of tracks that insist on pulling students along is the only practical solution.

>The challenge is what to do about the large number of students - at many schools the majority - who don't.

The solution isn't just to keep throwing money at the problem, because empirically that's been completely ineffective. If a large segment of the population are effectively learning nothing in e.g. the last 4 years of high school, they shouldn't be forced to attend, wasting resources that could be spent educating people who actually want to be educated. Instead there should be stronger support for people who come back to complete a high school diploma at a later age, as many of those students will come back with real motivation for study once they find their career opportunities without it are limited.