Tag Archives: Matthew Di Carlo

Student achievement and teacher evaluations: The math doesn’t add up?


Many states are applying for NCLB waivers. But they are adopting teacher evaluation criteria that are statistically, professionally, and morally inappropriate. As Education Week notes:

Federal officials say they have generally approved systems in which student growth counts for between 20 percent and 50 percent of a teacher’s evaluation. But also acceptable is a “trigger” mechanism, like one in Arkansas, where a teacher can’t be rated as effective if he or she fails to meet expectations for student growth.

Another acceptable method is a matrix system, like one in Massachusetts, in which student growth doesn’t receive a specific weighting but is coupled with other measures, such as unannounced teacher observations.

This would be fine if 20% to 50% (or more) of student achievement could be attributed to teachers. But decades of peer-reviewed research show that teachers are responsible for 10% to 15% of student achievement at best. The remaining influences on student achievement are other school factors (another 5% to 10%), non-school factors (60% or so), and random error (about 20%). As Matthew Di Carlo states:

though precise estimates vary, the preponderance of evidence shows that achievement differences between students are overwhelmingly attributable to factors outside of schools and classrooms.

Let’s simplify this even further:

  1. Decades of research show that teachers are responsible for 10% to 15% of student achievement
  2. State laws hold teachers responsible for 20% to 50% (or more) of student achievement
  3. Teachers thus are held responsible for 5% to 40% (or more) of student achievement over which they have NO CONTROL and negative consequences ensue under so-called ‘accountability’ schemes

Does anyone want to argue that this is fair or reasonable or valid?

This can’t be said enough: It is morally inappropriate (and probably illegal) for policymakers to evaluate teachers and hold them ‘accountable’ for factors beyond their control. But that’s exactly what appears to be happening in state after state after state.

In Iowa, lawmakers and our new Commission on Educator Leadership and Compensation are working together over the next year to formulate teacher evaluation criteria. Even if we somehow can become the first state in the nation to overcome all of the other statistical volatility and operational unreliability issues associated with tying teacher evaluations to numerical student learning outcomes, will we do what’s right and ensure that the student achievement component of teacher evaluations is at most 10% to 15%? If we do, will the federal government even let us? If we don’t, how long until the first due process lawsuit is filed?

[UPDATE: Be sure to see the 4 scenarios below. Which seems most fair to you?]

Image credit: 1+1=3, Austin Kleon