Luckily, my firm started collecting data on teacher aptitude some time ago, and basically you can separate all advanced math teachers easily into two categories: Okay with blacks in their classroom. Blacks and whites both end up succeeding at equal rates. Not okay with blacks in their classroom. Whites end up succeeding, blacks end up failing.

There are a number of research groups tracking teachers and student test scores. If such results had been released anywhere, wouldn't they be front page national news? And this seems like something that, e.g. the Gates Foundation would want known: if true, it's a magic bullet.

Why haven't academics and foundations studying teacher quality and value-added metrics reported such results?

A certain principle...remember that as principle of a school

The word is "principal."