> There was also a strong correlation between socioeconomic status and test scores. Students from higher income households and those who attended schools with more affluent students had higher scores.
The question is what was the delta within that group (and within other groups). Given we know that those of higher socioeconomic status do better than average, did they improve compared to their past selves, stay roughly the same, or degrade despite still maintaining above average results?
If, for example, they degraded, then it would indicate there is a problem happening that even the higher socioeconomic status doesn't protect from despite all its benefits (well it might protect relatively better that other SES, but not enough to prevent the downward trend).
If, instead, they improved relative to their past selves, it would indicate the problem causing the overall trend is found entirely within other SES groups (well not entirely, as it is possible the impact still hit this group but that other factors more than made up for it, but to keep it simple, we can ignore such a possibility unless we see even better data that can parse out these more complex relationships).
