I'm not sure if anyone has tried doing this as a going concern, but economists have done a pretty convincing (IMO) analysis of teachers value-add ex post. The m

I'm not sure if anyone has tried doing this as a going concern, but economists have done a pretty convincing (IMO) analysis of teachers value-add ex post. The most well known is the 2014 Raj Chetty paper. Seems to support your view. https://pubs.aeaweb.org/doi/pdfplus/10.1257/aer.104.9.2633 https://pubs.aeaweb.org/doi/pdfplus/10.1257/aer.104.9.2633