Students of unionised teachers do worse

This blew me away. I quote:

This paper examines the relationship between teacher unionization, student achievement and teachers’ pay using a cross-section of data from private schools in India. We use differences in student mark across subjects to identify within-pupil variation in achievement and find that union membership of the teacher is associated with reduced pupil achievement. We find no evidence this could be due to the unobservables not controlled for by this procedure. A school fixed effects equation of teacher pay shows that union membership raises pay and in this case too we find that remaining unobservables are unlikely to explain this outcome. We discuss the policy implications of the findings and show that the effectiveness of teacher credentials in improving teacher performance is linked to unionization.

Yes, this is in India, and that too in private schools, which are spasmodically governed. Now the results are fairly worrying for all people who are interested in improving education. Forget about government funded schooling, that’s neither the appropriate mechanism nor the argument here. The sample is important to note, mainly
English Medium private secondary schools in India which are generally the more privileged fee-charging
secondary schools. Many factors jump out.

• The negative impact of unionised teachers is less in states where the state government is also left oriented.
• If there is more competition in the form of more schools nearby, the negative impact is much larger.
• Higher teacher educational qualifications seem to only make a difference in the non unionised schools.
• Higher teacher salary and lower school classes make a bigger difference in non unionised schools rather than unionised schools.

What is the impact on the student? I quote the bloody amazing result:

we find that the achievement level of a student in a subject that is taught by a unionized teacher is about a quarter of a standard deviation lower than his/her achievement in a subject that is taught by a non-unionized teacher

What was shocking is that the authors point to a (unsubstantiated) conclusion, that only poor teachers join unions. Kindda makes sense, no?