Then I insert a
group of teachers (as Audrey described) who represent 20 % of a population and teach a disproportionate number of students who come from relatively lower socioeconomic, high
racial minority, etc. backgrounds, and I assume this
group is measured with negative bias on both indicators and this
group has a moderate
correlation between indicators of r = 0.50.
That is, only those teachers teaching classrooms inordinately stacked with students from
racial minority, poor, low achieving, etc.
groups might yield relatively stronger
correlations between their value - added and observational scores given bias, hence, the low
correlations observed may be due to bias and bias alone.