Good Teachers Leave

If we correct to a lower level and agree that "better" teachers are actually leaving DCSS because of the recent troubles how do we reconcile that with over 93% of teachers being rated "proficient" or "exemplary" even with the new more "objective" rating system? Sounds like a majority of teachers are on their way out the door. If you believe these ratings are inflated, and most folks do, just how many of "the best" need to leave before we've nothing left but teachers who were they ever subjected to an honest evaluation would struggle to be merely "ineffective"?