That is not mutually exclusive. First, you can absolutely sacrifice the median to improve the average. Second, I was pointing out when I think it started. One h

That is not mutually exclusive. First, you can absolutely sacrifice the median to improve the average. Second, I was pointing out when I think it started. One hypothesis is that the negative impacts of no child left behind and similar programs were initially mitigated/compartmentalized by the heavy academic tracking used at the time. My understanding is that much of this has changed over time with a reduction in number of tracks.