One of the most popular elements of the current business-model education reform movement (a movement to which I am vehemently opposed) is the use of Value-Added Models (VAM) to measure teacher effectiveness. Some states and districts are proposing the use of VAM to determine merit pay.
The simple version is this: The student is tested at the end of each school year. You take the kid’s score at the end of Year 1 and compare it to her score at the end of Year 2 and that tells you how much value the teacher has added, supposedly independent of factors like family, poverty, etc.
Diane Ravitch recently linked to an excellent piece written by mathematician John Ewing, president of Math for America, an organization dedicated to helping those non-Emmy Noethers among us to better understand — and apply — mathematics.
You should read his entire piece, because it gives an excellent rundown of where VAM comes from, how it was connected to education (and some of the early warnings that came with it!), and why it is problematic to link it to high stakes (like harsh penalties for kids, merit pay, or sanctions for schools).
The bit which jumped out most to me is from a report by the Economic Policy Institute, “Problems with student scores to evaluate teachers“. (Full disclosure: Ravitch is one of the authors of the report.) Among other things, the report notes:
For a variety of reasons, analyses of VAM results have led researchers to doubt whether the methodology can accurately identify more and less effective teachers. VAM estimates have proven to be unstable across statistical models, years, and classes that teachers teach. One study found that across five large urban districts, among teachers who were ranked in the top 20% of effectiveness in the first year, fewer than a third were in that top group the next year, and another third moved all the way down to the bottom 40%. Another found that teachers’ effectiveness ratings in one year could only predict from 4% to 16% of the variation in such ratings in the following year.
Think about that next time some politicians starts bloviating about how we need merit pay in order to get rid of all those “bad teachers”. (For the record: Yes, of course, some teachers suck. But merit pay and high-stakes testing are not good ways to fix that problem!)