Classroom Assessment Scoring System™

The Classroom Assessment Scoring System™ (CLASS™) is an observational instrument developed at the School Center for Advanced Study of Teaching and Learning to assess classroom quality in PK-12 classrooms. It describes multiple dimensions of teaching that are linked to student achievement and development and has been validated in over 2,000 classrooms. The CLASS™ can be used to reliably assess classroom quality for research and program evaluation and also provides a tool to help new and experienced teachers become more effective.

The CLASS™ system began as part of a national study in early childhood development. Eventually, that research grew in significance as education policies shifted focus to teacher accountability.

Teachers needed some way to see how their methods were working in the classroom. The CLASS™ instrument became a much-needed tool that could both effectively measure teacher-student interactions in a classroom setting and offer resources for strengthening those interactions across any subject area or age group.

CLASS™ is the only observational teacher-assessment tool that captures teacher behaviors linked to students gains and that has been proven to work in tens of thousands of classrooms, from preschool to high school and beyond.

The CLASS™ tool includes four cycles of 15-minute observations of teachers and students by a certified CLASS™ observer. Those observations are then rated using a manual of behaviors and responses. But it's never been just about measurement. It's about enhancing the overall relationship between teachers and students—and, therefore, the learning. After all, teachers have an influence that can extend beyond a classroom into a lifetime, and that's a role that few in our society have the privilege of playing.

Research conducted in over 3,000 classrooms concludes that from Pre-K programs into the third grade, children in classrooms with higher CLASS™ ratings realize greater gains in achievement and social skill development.

Current work focuses on expanding the CLASS™ into infant and toddler classrooms as well as validation work on Upper Elementary and Secondary versions of CLASS™. CASTL also supports the implementation of CLASS™ as a part of national (Office of Head Start), state (e.g., Virginia, Georgia, Arizona), and local (e.g., San Diego, Cal.) efforts to measure and improve early childhood education.


  • provides programs, schools, and districts with reliable, valid data on teacher effectiveness.
  • creates a common language about effective teaching practices across subject areas and grade levels.
  • helps teachers better understand how their interactions in the classroom affect student learning.
  • documents improvements in the effectiveness of teachers' interactions with students.

CLASS™ Resources for Education Practitioners:

Measuring and Improving Teacher-Student Interactions in PK-12 Settings to Enhance Students' Learning (pdf)

Why Should We Use Classroom Observation (pdf)

What Should Classroom Observation Measure (pdf)

How to Select the Right Classroom Observation Tool (pdf)

How to Use Classroom Observation Most Effectively (pdf)

How Classroom Observations Can Support Systematic Improvement in Teacher Effectiveness (pdf)

Learn about MyTeachingPartner™, a coaching program to help foster effective teacher-student interactions

Ongoing Research

CLASS: Optimizing Reliability and Validity and Classroom Observations

CLASS: Measures of Effective Teaching

Completed Research

Research Brief: Predicting Adolescent Achievement with the CLASS™-S Observation Tool (pdf)

Research Brief: Maximizing Classroom Time to Promote Learning

Additional Versions of the CLASS™

CLASS – Infant Version

CLASS - Toddler Version

CLASS: Secondary

CLASS: Individualized Classroom Assessment Scoring System (inCLASS)

Associated Faculty

Robert C. Pianta

Jason Downer


The Power of CLASS

What is CLASS

The Classroom Assessment Scoring System, developed at the Center for Advanced Study of Teaching and Learning is used nation-wide and globally.