[jkingsbery]

The facetious answer, of course, is that because the people designing these policies learned math in the California public school system.

Less facetiously: A/B tests are great at lots of things. But these results really shouldn't surprise anyone. The idea that you will improve things for one group of students by making things worse for another group is really not only silly, it cost real kids a year of potential progress. An A/B test would cost some percentage of kids that year, which is better than hurting the whole group, but A/B testing on something that obviously would hurt their future does not seem fair to those hurt by the proposed changes.