In 21st century classrooms, teachers are encouraged to focus on students as thinkers. In order for students to know and understand how to get better at their thinking, teachers must use an assessment and feedback system that accurately represents these processes. Traditional assessment tools, rubrics, and performance assessments often assess only content and/or product. This session demonstrates how to assess thinking using criteria that are quantitatively and qualitatively specific, measureable, and observable against evidence. How to assess higher-order thinking in a single formative or summative assessment as well as document growth over time is also addressed.