The Dallas experiment is interesting, and it’s not surprising at all that the students actually learned more than if they had been in less-advanced classes. The question I have is what the grades look like for the kids who were somewhat involuntarily included in the class. In junior high, grades don’t matter all that much, but come high school it could be worse to have lower grades in more challenging courses, depend…
I understand that grades matter for getting into college, but this mindset is viscerally horrifying to me. It almost reads to me as: "What if people were appropriately challenged and learned more? Wouldn't that be horrible?" Grade inflation is a terrible thing, even if it is likely an intractable problem because of the incentives that go into it.
It doesn't take too many parent-teacher conferences to figure out that the parents that ask for parent-teacher conferences want to see "the line go up" and aren't necessarily concerned with their children being challenged or learning much of anything.
The squeekiest of those wheels move from parent-teacher conferences to parent-administrator conferences (and sometimes parent-lawyer-administrator conferences) and you end up with school-wide policies like failure quotas where you are not allowed to have more than 5% of your students fail your class (ie the responsibility of the students grade falls on the teacher, not the student). And that is how grades stop being a measure of a student's understanding of the material.