Step 1: The value-added scores also fluctuate between years. A teacher who gets a particular ranking in year one is likely to get a different ranking the next year. There will always be instability in these rankings, some of which will reflect “real” performance changes.
Step 2: However, it is very hard to have trust in any performance rating if you have a better shot at a coin toss rather than getting the same rate the next year.
(But it is difficult to trust any performance rating if the odds of getting the same rating next year are no better than a coin toss.) original
Step 3: Any teacher who winds up in the forty-third percentile in comparison to his/her peers could technically be somewhere in the middle of the fifteenth and seventy-first percentile. (Ravitch 270).
Step 4: In a study to determine teacher’s in New York City margin of error, economist, Sean Corcoran found their margin of error was a little above or below twenty-eight points. (Ravitch 270).
Step 5: It is very unlikely that a teacher will have the same rating consecutively and there are always other aspects and variables to be accounted for. “But it is difficult to trust any performance rating if the odds of getting the same rating next year are no better than a coin toss.” (Ravitch 271).
Diane Ravitch, The Death and Life of the Great American School System(New York: Basic Books, 2011), pp. 270-71.