“If you get unprepared students in your class and they don’t do well, how does that get explained?”
From "Thoughts on Junk Indicators, School Rating Systems & Accountability":
"The measures we take can be referred to as “realizations” which are generated by underlying processes (all the stuff going on in school, as well as in the daily lives of the children attending and teachers working in those schools, inclusive of weather conditions, heating, cooling and lighting, home environments, etc.)."
This will be true of all assessments--but I doubt that there's many people who adopt that perspective (that nothing short of the whole context is an explanation). Our brains can't handle that, of course, but in the search of simplifications, losing sight of this risks inhibiting our humility.