Formative assessment, along with effective feedback, is one of the most impactful parts of teaching and when done well, it can foster significant improvement.
What is formative assessment?
Formative assessment is any learning activity which reveals information to teachers and learners which can be used to improve learning. This is distinct from summative assessment, the intent of which is to provide terminal grading. Formative assessment allows teachers to understand where a learner is currently 'at', so that the teacher can a) adapt future instruction to better meet learning needs b) consider differentiating their support, and c) enable effective feedback to and between learners.