This report outlines three educational approaches: (a) "traditional," the currently dominant approach, a largely lecture-oriented, authoritarian style that makes heavy use of assessments "of" learning, which are useful for accountability purposes but only marginally useful for guiding day-to-day instruction; (b) "progressive," a highly student-centered approach that relies on assessments "for" learning, which can be very useful in guiding day-to-day instruction; and (c) "unified," a new, integrated approach that uses the best of both kinds of assessments--"for" and "of" learning--and which leverages computer technology, educational measurement, and cognitive science to address factors that undermined earlier attempts to implement the progressive approach. This report examines some of the research, trends, and factors that should be considered, understood, and, in some cases, leveraged, in order to move toward the unified approach. Further, this report presents examples of how ETS projects are moving toward the new approach to harness assessment in the service of learning.