What do other researchers have to say about the recent trends in learning and schooling?
The decline (and rise) in student test scores over the last twenty-five years is one of the most researched and least understood phenomena in education. As yet, researchers have produced no simple or adequate explanation for the initiallytroubling, then temporarily encouraging, trends in test scores. The trends appear to be the product of many factors, some educational but many non-educational. The most important factor, accounting for perhaps a fifth of the total decline, appears to be a change in the ethnic composition of the test-taking population.  American schools were taking in different kinds of students, students who were more difficult to educate than students in the past. Influences in the home were also changing. The second most important cause of the decline and upturn appears to be changes in family size, with larger families initially hampering achievement and then smaller families encouraging it.
It is also clear that the decline did not affect all grades equally. The decline was comprised primarily of worsening scores among students born before 1963, the "baby boom" generation.  As these students moved through the schools, test scores declined, pushing SAT scores down from 1964 to 1979. But as the baby boomers began to be replaced, around 1970, by a new cohort, the "baby bust" generation, test scores in the early grades began to climb. By 1980 the younger cohort, now in high school, was taking the SAT tests, and posting the modest increases in SAT scores observed during the early eighties. Unfortunately, further gains have not been posted by subsequent cohorts, leaving achievement generally below the levels of twenty-five years ago.
The significant contribution of so-called compositional and cohort effects to changes in test scores highlights the importance of factors beyond the control of schools in producing student achievement. Yet, even when the full range of non-educational factors is taken into account – alcohol and drug use, and exposure to environmental lead (both of which had small effects on test scores); single-parent households, maternal employment, and television viewing (none of which had any effect on test scores) – no more than a third of the variation in test scores over time can be explained.  That leaves a lot of room for educational factors to make a difference.
But researchers have made little progress in identifying significant educational factors. The most comprehensive study to date, by the Congressional Budget Office in 1987, found some evidence that schools might have undermined achievement by watering down the content of courses, assigning less homework, and using less challenging textbooks.  But the study found no impact, positive or negative, from other educational factors such as teachers' test scores, teachers' educational attainment, or state graduation requirements. The fact of the matter is, most of the relationship between schooling and learning over the last twenty-five years remains a mystery.
Some clues about the relationship can be found, however, in other kinds of research into student achievement, research that has not focused on test score trends but on differences in tests among schools at any given time. This research has reached some fairly strong, though negative, conclusions about the connection between schooling and learning. This research implies that there is no surprise in the fact that test scores declined or stagnated while school resources and certain school conditions improved. A recent survey of 147 statistical analyses of school performance, for example, found no consistently positive and significant relationship between student achievement and any of the major factors popularly assumed to influence achievement: teacher-pupil ratios, teacher education, teacher experience, teacher salaries, and per-pupil expenditures.  In other words, much of what school systems were doing to turn test scores around may have no systematic effect on school performance.
Nevertheless, we know that factors outside of schools do not adequately account for student achievement either. And we know from casual observation, as well as careful case studies, that some schools are much, much better than others. The challenge remains to find out why. The research in which we have been engaged takes up that challenge.