Getting good metrics is hard.
Garbage in, garbage out.
One of the stories linked makes interesting reading: https://www.washingtonpost.com/local/education/creative--motivating-and-fired/2012/02/04/gIQAwzZpvR_story.html
Basically the value-added "measurements" conflicted with other assessments but were allowed to dominate the assessment. Digging in a little deeper it turns out that the start of year measurements weren't the school's own, they were someone else's. Right there is a prerequisite for using numerical approaches - you've got to be sure you can rely on the data.
The article ends “Teaching is an art,” she said. “There are so many things to improve on.”
Measuring is also an art.