Some of us would point to political pressures to evidence higher "success" in terms of increased graduation rates, which wind up pressuring institutions to reduce standards and pass students regardless of whether they've mastered material skills or not.
Note that U.S. high school graduation rates have been spiking upwards in recent years, which provides opportunities for systems and states to congratulate and defend themselves:
Image from Wikipedia. Note this is in the context of an article discussing how college graduation rates are failing to increase significantly in the same time frame.
Here's an article on the CUNY (City of New York) University Faculty Senate blog in 2017 summarizing this trend towards higher-graduation-from-high-school, but lower-preparation-for-college rates, with a number of interesting links for further reference:
Both the State and the City of New York have recently reported a rise
in high school graduation rates. But college preparedness still
leaves much to be desired. It presents a major challenge for colleges
that admit students whose reading, writing and mathematical skills are
not at the level needed for academic success.
Close to 80 percent of the Department of Education (DOE) graduates
entering CUNY in the Fall of 2015 needed remediation of some kind.
While the NYC DOE cites a 79 percent graduation rate as evidence that
schools are improving, only an average 37 percent of students graduate
college-ready...
Both the State and City have been altering their standards for
graduation to boost those numbers. Now CUNY has changed its
requirements and methods for placing people into remedial classes.
What this portends remains to be seen for students just entering into
credit bearing courses with skills that are even lower than in the
recent past. One strategy is to provide a non-algebra path to a
degree. Such intellectual skills and mental habits as might be
inculcated by the mastery of algebra are thus being set aside in the
hopes that those no longer burdened by graduation requirements
including algebra will graduate and find some sort of employment.
Indeed, since that blog post was written, CUNY has waived the requirement for an elementary algebra skills test (at roughly the 9th grade level) that was previously required for graduation -- precisely because it was found to be impossible to structure such an exam in a way that everyone would pass it. Moreover, they've eliminated all entry-placement tests and remedial courses (leading the way among other large institutions in the U.S.); this disposes of the embarrassment around the "percent [who] needed remediation" number, as it simply doesn't exist anymore. And they've declared by fiat that all students will be entered to college-credit bearing classes regardless of skill level. For example, from a 2019 university memo on the new "corequisite" course model (emphasis as in original):
The college must allow enrollment of students who are not skills proficient.
Scherer & Anson in their book Community Colleges and the Access Effect make the point that high schools practically guaranteeing graduation, and community colleges guaranteeing acceptance via open admissions, set up students to not perceive hard work as a requirement (Chapter 8; quoting from Skelly & Laurence, "Tracking College Readiness", The School Administrator 2011):
Community colleges’ open enrollment policies have a negative effect on
student motivation during high school particularly during the senior
year. Seniors going to a “JC” (junior college) know their admission is
guaranteed, so they often slack off and avoid challenging course work,
particularly during their senior year. The bad habits formed in high
school are not easily shaken.
In light of this perceived end-game to the political pressure for increased graduation rates (previously at high schools, and now at least at lower-level, public-funded colleges), we might reflect more generally on what is known as Campbell's Law:
The more any quantitative social indicator is used for social
decision-making, the more subject it will be to corruption pressures
and the more apt it will be to distort and corrupt the social
processes it is intended to monitor.
