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What is value-added?

Measuring a teacher’s impact on student learning can be challenging. After all, students start the year at different skill levels, and they all face different factors inside and outside the classroom that affect how they learn. 

At its core, IVA is a way of dealing with these challenges. It helps us estimate the teacher’s impact on student learning as opposed to the impact of other factors, such as students’ prior skill level, the resources they have at home, any learning disabilities they may have, or their classroom composition. 

In short, IVA helps us understand what the teacher did, apart from everything else.


How and why does DCPS use value-added data?

DCPS uses value-added data as part of IMPACT, our system for assessing teacher performance. We do so because we believe that clear evidence of student learning is an essential part of being an effective teacher. 

Individual Value-Added (IVA) applies to English language arts teachers in grades four through ten, and to math teachers in grades four through eight. These teachers are in IMPACT Group 1. IVA is restricted to these grades and subjects because they are the only ones for which we have student DC CAS scores from both the prior and current year, a requirement for value-added.

How does value-added work?

First, we calculate how a teacher’s students are likely to perform, on average, on our standardized assessment (the DC CAS) given their previous year’s scores and other relevant information. We then compare that likely score with the students’ actual average score. Teachers with high IVA scores are those whose students’ actual performance exceeds their likely performance. This process is explained in further detail in IVA section of the Group 1 IMPACT guidebook (see link below).

Please note that the value-added calculation process is quite complex, which is why DCPS has contracted with Mathematica Policy Research, a nationally respected research firm, to conduct the analyses. Mathematica’s clients have included the U.S. Department of Education and many other federal, state, and local agencies.

In addition, independent value-added experts reviewed the methodology used to evaluate DCPS teachers, including Eric Hanushek of the Hoover Institution at Stanford University, Jonah Rockoff of Columbia Business School, and Tim Sass of Georgia State University.

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