Is the impact of NGA on index values desirable?

Raised by: OEAA itself, in Session 3 — Accountability Growth Methodology Targets.

The situation. The content-area model application scatterplot showed a meaningful impact on overall rating, and the English Learner application showed the same magnitude of impact on the EL Index. OEAA “has not determined if this is a desirable impact and would need to take some time to research this.”

Why it is the hard question. The Nearest Grade Average Method was proposed to fix over-identification of high schools. Whether it fixes the problem or merely moves it depends on where the identifications land after the change, and on whether the schools newly identified are ones anyone believes should be. A method that produces more reasonable targets and less defensible identifications is not obviously an improvement.

Note that this question interacts with Set adequate growth above the 65th percentile: raising the adequacy threshold at the same time as adopting NGA would change the impact again, in the opposite direction.