I believe the issue is measures of 'achievement' and 'excellence' typically use the 20th and 50th percentiles, respectively. For example, most education studies focus on what improves graduation rates, passing rates, or the bottom 10–20% on standardized assessments. Most school districts' financial incentives rely on these metrics as well. Occasionally you'll get a study that looks at the median (and even more rare, the 90th percentile), but no standardized assessment even showcases the bellends of the distribution. This is why you get claims like this

> High-achieving kids are doing roughly as well as they always have, while those at the bottom are seeing rapid losses

in the article, when they're actually doing much worse as well, which can be seen from the median (or top) scores in STEM competitions. All the financial incentives are for schools and teachers to focus on their bottom 20% of students, and even if they cared about their top students (culturally, most education departments do not), it's not even feasible to collect that data, short of signing everyone up for the AMC 12. So, naturally, the percent of elementary schools offering gifted programs has declined by fifteen (twenty?) percent in the last twenty years, and the general standards and curricula have been lowered to teach to the 20th percentile. This also creates a cultural issue where many students recognize they're bored, and that schools are not trying to teach them, so they become disaffected and stop caring. My friends in high school joked that school was for socializing, and frankly, what other purpose does it serve anymore for most kids?