Diagnostic Math Assessment: A Practical Guide for Educators and Parents A diagnostic math assessment is a targeted evaluation that identifies exactly where a student’s knowledge breaks down, which misconceptions they carry, and what they are ready to learn next — not a grade, but a map. Once you have that map, the next steps are clear: Administer a topic-screener with a moderate number of items that covers the key skill domains for the student’s grade band (number sense, fractions, algebraic reasoning, geometry). Request or generate a topic-level report, not just a total score, so you can see precisely which concepts need attention. Group students or plan sessions by skill profile rather than by overall performance level. Use tools with documented reliability and validity evidence, such as i-Ready Inform (Curriculum Associates) for K–8 adaptive reporting or Math Mammoth placement tests for curriculum-aligned gap analysis. Table of Contents What does a diagnostic math assessment actually measure? How does diagnostic testing differ from formative and summative assessments? When should you give a diagnostic, and how often? What formats and tools are available for math diagnostics? How