What type of assessment primarily measures students' understanding throughout instruction?

Formative assessment is designed to monitor student learning and understanding during the instructional process. This type of assessment provides ongoing feedback that can be used by both teachers and students to identify areas that need improvement and to inform teaching practices. It often involves informal assessments such as quizzes, class discussions, and observation, allowing educators to adjust their instruction in real-time based on the students' needs.

In contrast, summative assessments are conducted at the end of an instructional period to evaluate what students have learned, rather than providing insights throughout the learning process. Standardized assessments are designed to measure student performance against a common standard, often focusing on accountability rather than individual student understanding during instruction. Diagnostic assessments typically take place before instruction begins to identify students’ strengths and weaknesses, rather than during the learning process itself. Thus, formative assessment is the best choice for measuring students' understanding throughout instruction.