I used to be a teacher also, but in a college level trade school, in a state that consistently ranks near the top in high school scores, in a rural, white, midwestern middle class district that had sufficient funds to produce state champion football teams, where there were minimal poverty and social issues and minimal crime.

I still had a steady stream of high school graduates showing up in my college program that could not read a paragraph, could not write a sentence, who could not add, subtract, multiply or divide fractions or decimals, yet they were proud gradates of the local school district.

What's broke? No idea, but I do know that if that district had done even the most trivial of standardized testing, those students would have been flagged for remedial work long before they started college. Instead the college, with about 40 full time faculty, dedicated 3 of those faculty to 4th through 8th grade remedial math and reading.

"No idea, but I do know that if that district had done even the most trivial of standardized testing, those students would have been flagged for remedial work long before they started college."

Unless you taught a long time ago or are in a very strange state, odds are those children were tested with standardized tests, probably multiple times. I live in Michigan, so I can guarantee that pretty much every child coming out of Detroit has been tested in a standardized manner by the state at least three times while in school (conservatively, I remember having more but I'm not sure what all they were), and they still come out with problems. You can't even get a real HS diploma without passing these tests. (At least when I graduated you would get a diploma from the school but it lacked some sort of state endorsement.)

I don't think total lack of standardized testing is the problem. The problem is they are either being cheated on or gamed, or nobody really knows how to solve the problems being identified.

Having to pass tests prior to getting a diploma is a recent thing, at least to old dudes like me.

I stopped teaching twenty years ago. There were standardized tests in high school, but they were not used to determine progress or as graduation requirement. Social promotion was common - students were not held back under any circumstances, as it was assumed that the social stigma would be worse than the failure to actually learn anything.

We tested the students at the time they applied to college. Because were were publicly funded, open entry, we accepted all high school graduates regardless of how they scored. If they scored low, we moved them into remedial programs/courses.