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.