> the only teacher of highest track Algebra II class at a local HS
Being the only teacher of the highest track Algebra II class in the school means that anyone who wanted to take the highest track Algebra II class--which plausibly contains many of the best math students--would have to take it from this teacher.
The whole point of the kind of value added modelling that is the centre of this case is that it attempts to factor out things like the quality of the student to estimate the quality of the teacher, precisely so that bad teachers who by dint of circumstances are associated with high-performing students don't get high ratings.
The problem is that if student background counts for the greater part of performance even a good teacher may have difficulty scoring highly if they happen to get a "good" class (one that scores highly on student quality.)
On a larger scale, the anecdote we are discussing here suggests that teachers as individuals may not make that much difference to student's performance, since this bad teacher was still able to turn out the best performing students thanks (one is supposed to presume) selection effects alone.
> the only teacher of highest track Algebra II class at a local HS
Being the only teacher of the highest track Algebra II class in the school means that anyone who wanted to take the highest track Algebra II class--which plausibly contains many of the best math students--would have to take it from this teacher.
The whole point of the kind of value added modelling that is the centre of this case is that it attempts to factor out things like the quality of the student to estimate the quality of the teacher, precisely so that bad teachers who by dint of circumstances are associated with high-performing students don't get high ratings.
The problem is that if student background counts for the greater part of performance even a good teacher may have difficulty scoring highly if they happen to get a "good" class (one that scores highly on student quality.)
On a larger scale, the anecdote we are discussing here suggests that teachers as individuals may not make that much difference to student's performance, since this bad teacher was still able to turn out the best performing students thanks (one is supposed to presume) selection effects alone.