Updated

After three years of research on measuring teacher performance, the Bill & Melinda Gates Foundation says it takes multiple measures to most accurately judge educators.

The Seattle foundation concluded in its final report on its Measures of Effective Teaching research that test scores or principal evaluations are not enough on their own. The findings mirror what teachers unions have been saying. The report was released Tuesday.

The federal government has been pushing states to update their teacher evaluation systems because it felt existing systems were inadequate. At the same time, the Gates Foundation was studying these issues, saying it wanted to add to the discussion. Most states and big city districts have adopted some elements of the recommendations.