Give credit where credit is due.

Yes, but. From Achievement Gap Between Rich and Poor Public School Students Unchanged Over 50 Years
Spending four times more in real dollars per pupil doesn't compensate for low-quality teaching. by Ronald Bailey.

I empathize with the sentiment but I think it is also, to a degree, unfair. We have made an unconscious trade-off decisions which in part explains some of the data. From the article.

Half a century of trying hasn't closed one of schooling's most vexing achievement gaps. According to a new paper, the gap in educational achievement between public school students in the bottom 10th socioeconomic status (SES) percentile and those in the top 90th SES percentile has remained essentially unchanged over the last 50 years.

"In terms of learning, students at the 10th SES percentile remain some three to four years behind those in the 90th percentile," report a team of researchers led by the Stanford economist Eric Hanushek in their disheartening new National Bureau of Economic Research study, "The Unwavering SES Achievement Gap."

It would be one thing, the researchers note, that "if all achievement were rising, i.e., if a rising tide was lifting all boats." But that's not what's happening. Young adolescents' performance has risen over the past 50 years, but their scores drift downward once they reach high school. The upshot is that there has been no significant improvement in the overall education achievement scores of American high school student cohorts born since the 1950s.

The researchers draw upon data from four periodically administered assessments of U.S. student performance: the Program for International Student Assessment, the Trends in International Mathematics and Science Survey, and two versions of the National Assessment of Educational Progress. They then divvy up the student cohorts based their parental socioeconomic status.

The researchers calculate the standard deviation between the scores of each socioeconomic cohort to compare how far the average achievement scores of students clustered in the top 10 and 25 percent of SES percentiles are from the scores of those students aggregated into the bottom 10 and 25 percentiles of SES. A declining standard deviation would mean that the gaps between the cohorts' scores are closing. That is not what they find.

As they report at Education Next, the socioeconomic achievement gap among the 1950s birth cohorts is very large—about 1.0 standard deviations between those in the top and bottom deciles of the socioeconomic distribution (the 90–10 gap) and around 0.8 standard deviations between those in the top and bottom quartiles (the 75–25 gap). Measuring cohorts of students born since the 1950s, the SES gap closes by about 0.5 standard deviations for students under age 14. But those gains among young adolescents disappear almost entirely by the time students reach age 17.

The persistence of the SES gap remains when the researchers compare only white students over time, and they take into account such factors as the changing ethnic makeup of American school children.

The researchers note that these disappointing results occurred despite the fact that "overall school funding increased dramatically on a per pupil basis, quadrupling in real dollars between 1960 and 2015." In addition, pupil-teacher ratios declined from 22.3 in 1970 to 16.1 in 2014.

I cannot prove it but my suspicion is that part of the explanation is that we have had a prolonged period of immigration from countries with lower national IQ averages and lower education attainment countries to the US. This change of immigration policy occurred in the 1960s, matching the time frame being examined. We have gone from 5% foreign born to 15% foreign born in that time frame. That is for the population as a whole. I think the numbers are higher for the younger school grades.

If you accept that it is going to cost more to educate children in the English language, social norms of America, deal with any accumulated education deficits from wherever they originated, etc., then it makes sense the cost of education might rise while overall results remain flat.

In addition, the fact that Americans of respective broad cultural backgrounds, when compared to home origins (white Americans to Europe, Hispanics to Central and South America, Asian Americans to Asia) materially outperform their home countries' international PISA scores suggests that perhaps American education is doing a good job but it is dealing with a much more heterogeneous population by culture and by immigrant status.

It is easy to slap teachers around and lord knows there are plenty of instances of ineffective teachers and ineffective schools, but we should also acknowledge what to me appears to be a real accomplishment.

One thing I never see in these studies and which I would dearly like to know, is whether schools are effective at serving as mobility platforms. To do so, we would need to look at IQ as well as SES. My suspicion is that we do a pretty good job of finding and redirecting top quartile IQ talent from low quartile SES. Low SES status may have many vectors influencing school accomplishment but if high IQ talent from low quartile SES are actually accelerating past their circumstances, that would be great news. I suspect that is happening but I do not know it is.