What does the research tell us about the power of formative assessment?

Formative Assessment and the Design of Instructional Systems (Sadler)

"...the learner has to (a) possess a concept of the standard (or goal, or reference level) being aimed for, (b) compare the actual (or current) level of performance with the standard, and (c) engage in appropriate action which leads to some closure of the gap." 

The Role of Assessment in a Learning Culture (Shepard)

"Student self-assessment services cognitive purposes, but it also promises to increase students' responsibility for their own learning and to make the relationship between teachers and students more collaborative."

Formative Assessment and the Next-Generation Assessment Systems: Are We Losing an Opportunity?(Heritage)

"Only by keeping a very close eye on emerging learning through formative assessment can teachers be prospective, determining what is within the students’ reach, and providing them experiences to support and extend learning. Through these experiences students will incorporate new learning into their developing schema." 

The Power of Feedback (Hattie and Timperley)