I've written before about gender bias in student evaluations of teaching (see here, with more to come soon in a future post). There is good reason to worry that student evaluations don't even measure teaching quality (see here, with more on that to come too). However, it turns out that it isn't just students that are biased in evaluating teachers. This article by Sabrin Beg (University of Delaware), Anne Fitzpatrick (University of Massachusetts, Boston), and Adrienne Lucas (University of Delaware), published in the AEA Papers and Proceedings last year (ungated version here), shows that primary school principals, at least in Ghana, are biased as well.
Their data come from the Strengthening Teacher Accountability to Reach All Students (STARS) project, a randomised trial that collected data from 210 schools in 20 districts in Ghana. They asked fourth and fifth-grade teachers to rate their own performance (by comparing themselves to teachers at similar schools), and asked principals to rate their teachers. They also presented teachers and principals with vignettes, where the gender of the teacher described was randomised, and asked the principals to rate the teacher described in the vignette. Finally, they measured the 'teacher value-added' using standardised tests administered at the beginning and end of the year. Comparing ratings between male and female teachers, Beg et al. find that:
Female and male teachers were equally likely to assess themselves as at least more effective than other teachers at similar schools... In contrast, principals were about 11 percentage points less likely to assess female teachers this highly relative to male teachers...
The gender bias of principals was not statistically significant though (a point that Beg et al. do not note in the paper, preferring to concentrate on the magnitude of the coefficient). They also:
...test for gender differences in the objective measure of effectiveness based on student test scores and find that female teachers had on average 0.28 standard deviations higher effectiveness than their male peers...
This puts the statistical insignificance of the principals' gender bias into more context. Using an objective measure of teacher value-added, female teachers are better teachers than male teachers, and yet female teachers are not statistically significantly rated any better than male teachers by principals. No difference in subjective assessments, when objective assessments say that female teachers are better than male teachers, provides evidence of bias.
Coming to the vignettes though, Beg et al. find that:
Principals further demonstrated evidence of bias against women in their hypothetical assessments. Principals rated individuals 0.12 standard deviations less effective when they had a female name instead of a male one...
Again, the difference is not statistically significant (and doesn't provide strong evidence of bias, because there was by construction no difference in teacher quality between male and female teachers in the vignettes). Overall, I was a bit surprised by this study, because when Beg et al. graph principals' subjective assessments of male and female teachers against the teacher value-added, you get this (their Figure 1):
At every level of objective teacher value-added, male teachers (the black line) are subjectively rated better than female teachers (the blue line) by principals. And yet, the difference is statistically insignificant in Beg et al.'s regression model. Perhaps Beg et al. should have included the objective measure in their models (or included confidence intervals in their Figure 1). Overall, this provides some weak additional support for gender bias in the evaluation of teachers.
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