"Formative assessments are ongoing assessments, observations, summaries and reviews that inform teacher instruction and provide students feedback on a daily basis." (Fisher, D. & Frey, N, 2007. Checking for Understanding: Formative Assessment Techniques for Your Classroom, ASCD). Any assessment used to inform instruction is a formative assessment. Just as a medical doctor must examine a patient prior to prescribing treatment, teachers must assess a student's level of understanding pertaining to the learning target prior to determining appropriate instruction. Throughout instruction, checks for understanding guide instructional decisions for all students, regardless of achievement level.
"While assessments are always crucial to the teaching and learning process, nowhere are they more important than in a differentiated classroom, where sudents of all levels of readiness sit side by side. Without the regular use of formative assessment, or checks for understanding, how are we to know what each student needs to be successful in our classroom? (Dodge, J. 2009. 25 Quick Formative Assessments for a Differentiated Classroom, Scholastic Inc.)
"We use the general term assessment to refer to all those activities undertaken by teachers -- and by their students in assessing themselves -- that provide information to be used as feedback to modify teaching and learning activities. Such assessment becomes formative assessment when the evidence is actually used to adapt the teaching to meet student needs." (Black, P. & Wiliam, D. 1998. Inside the Black Box: Raising standards through classroom assessment, King’s College, London)
"Assessment for learning can contribute to the development of effective schools. If assessments of learning provide evidence of achievement for public reporting, then assessments for learning serve to help students learn more. The crucial distinction is between assessment to determine the status of learning and assessment to promote greater learning." (Stiggins, R. J. 2002. Assessment Crisis: The Absence of Assessment FOR Learning, in Phi Delta Kappan Vol.83, No.10 pp 758-765.)
"An assessment functions formatively when evidence about student achievement elicited by the assessment is interpreted and used to make decisiosn about the next steps in instruction that are likely to be better, or better founded, than the decisions that would have been made in the absence of that evidence." (William and Black, 1995). According to Black and William (2009), effective formative assessment is comprised of five key strategies:
engineering effective classroom discussion, questions and learning tasks that elicit evidence of learning;
providing feedback that moves learners forward;
clarifying and sharing learning intentions and criteria for success;
activating students as owners of their own learning; and
activating students as instructional resources for one another.
The list of tools that support the five strategies is extensive. Formative assessments such as Exit Cards, Audience Response Systems, Cambridge Note-taking, Carousel Brainstorming, Find Someone Who, Quick Write/Quick Draw and Thinking Maps are just a few examples of tools that can be used when checking for understanding.
The importance of Classroom Assessemnt for Student Learning (CASL) is further explained by Jan Chappuis of the Assessment Training Institute.