Analogies are important. While often imperfect, they help us make connections and better understand our world.

That’s why I think it’s a shame the education field has yet to come up with good analogies for value-add data and models, especially in the teacher evaluation context. For example:

  • Is value-add like a high-school GPA, providing a threshold for certain decisions (you can’t get into College ABC without a certain GPA) but best used in conjunction with other factors (were you a varsity athlete? Do you do community service? How was your admissions essay?)
  • Is value-add like a batting average, telling us how good teachers are at some skills (hitting), but not others (fielding)?
  • Is value-add like a credit score, highly dependent on input qualities (did the bank get everything right?) with the potential to change over time (decreasing when you took on student loans, increasing as your credit history grows)?

The inability of education reformers to clearly explain value-add has confused the conversation. For example, yesterday I went to a terrific conference sponsored by the National Center for the Analysis of Longitudinal Data in Education Research (a mouthful! – so they go by CALDER). The brightest minds in education research presented papers on value-add. But it was clear that throughout the day, the non-researchers in the audience struggled to grasp the policy implications. In a somewhat tense moment (as these things go), an audience member suggested that value-add doesn’t take into consideration x situation so it can’t be used by itself to assess teachers, to which an exasperated panel member replied “I just heard [my colleague] say that!” Something was clearly lost in translation – an analogy would have been useful (JF).

What analogies would you offer for value-add?