Regarding test scores, and this is something I know a lot about. I've been an adjunct professor at 2 local colleges for several years, and I have noted a generational shift towards dumbing it down, lowering the bar and ensuring everyone gets a passing grade. Administrators at for profit colleges are especially "guilty' of this.
I've taught classes where 20 somethings were full of angst and drama because they werent going to make an "A" in my class, and they were used to getting "As" in the other classes. None of these students were above average; they were all "C" students but were being given passing or better grades due to the dumbing of the system. To think that they were used to getting "As" was an insult to me. And this was college folks; some of these students were a semester or two away from graduating.
I have another experience which will shed light on the mother jones test scores to show how irrelevant they are. In my past relationship the woman had two sons, a year apart, who attended elementary and middle schools. These were considered very good schools with good programs and teachers (high socio-economic area). For several years running both of these young men were placed in advanced math and other classes at the beginning of the school years based on the previous years (the tests were administered at the end of the previous shool year) standardized test scores. They were scoring high in math and other topics even though they had to drop the advanced placement classes within a few months because they were woefully inadquate. They didn't get stupid over the summer. The problem is something I faced as an adjunct.
It is called teaching to the test and it is dishonest and has no place in academia. But since standardized test scores drive funding from state and federal coffers and an improvement on test scores gets teachers and administrators raises and praise, guess what they have begun doing? Teaching to the test. Many, if not most, are preparing the students just in advance of the test dates on sample tests. I had the same pressue as an adjunct, as the Millenials were used to being given the exact questions and/or answers in advance. So mother jones figures are more than skewed; they are to me worthless.
Several scandals have been uncovered about this topic; google it and you can see that it is a nationwide problem. I would compare it to the steroid issue in baseball; an asterisk should be place next to all of it.