This is the corporatist way. Everything is measured so it can be 'tweaked' by managers and technocrats because school is a business now.

Having a bad teacher to me doesn't matter when any kid can turn on his phone or laptop and watch free MIT lectures, free Stanford lectures, free Khanacademy lectures, free Android and iOS developer courses all over youtube, ect.

Gates obsession with teacher metrics would be better spent on building an entirely free university with worldwide standardized credits, so somebody in Pakistan can have their education credentials accepted should they start working overseas instead of being forced to drive a cab around Montreal while spending thousands to retake what he/she already learned.