For several generations now, efforts to improve student achievement in the United States have been tied in some way to test scores (Koretz & Hamilton, 2006). Large-scale testing programs at the state level have varied in purpose and design, but they share the view that test scores should have a central role in monitoring and evaluating student learning. The prominent position of tests in current efforts to improve education has made instrument quality a critical concern. The purpose of this chapter is to describe contextual factors in assessment programs that have direct effects on the quality of measures used for accountability and to consider ways in which accountability systems can provide for enhanced assessments of student learning.