The Classroom Assessment Scoring System (CLASS®) is an observation instrument that assesses the quality of teacher-child interactions in center-based preschool classrooms. CLASS® includes three domains or categories of teacher-child interactions that support children's learning and development: Emotional Support, Classroom Organization, and Instructional Support. Within each domain are dimensions that capture more specific details about teachers' interactions with children.

The CLASS® dimensions are based on developmental theory and research suggesting that interactions between children and adults are the primary way of supporting children's development and learning, and that effective, engaging interactions and environments form the foundation for all learning in early childhood classrooms.

CLASS® is scored by trained and certified observers using a specific protocol. Following their observations of teacher-child interactions, CLASS® observers rate each dimension on a 7-point scale, from low to high.

• Scores of 1-2 mean the quality of teacher-child interactions is low. Classrooms in which there is poor management of behavior, teaching that is purely rote, or that lack interaction between teachers and children would receive low scores.
• Scores of 3-5, the mid-range, are given when classrooms show a mix of effective interactions with periods when interactions are not effective or are absent.
• Scores of 6-7 mean that effective teacher-child interactions are consistently observed throughout the observation period.

During the CLASS® observation reviewers independently review and score each classroom using a computer-based scoring system in the Office of Head Start Monitoring Software (OHSMS). After the review OHSMS averages the scores across the grantee to result in grantee-level dimension scores. The dimension scores are then used to calculate the grantee-level domain scores. Reviewers do not have access to the grantee level score during or after the review.

Emotional Support assesses the degree to which teachers establish and promote a positive climate in their classroom through their everyday interactions.

Classrooms that score well in this domain have teachers that are responsive to children, acknowledge children's feelings or emotions, help children resolve problems, redirect challenging behavior, and support positive peer relationships. Observations provide evidence that teachers and children support and respect one another. Teachers are aware of and respond to children's academic and emotional needs and consistently provide comfort, reassurance and encouragement. There is an emphasis on children's interests, motivations and points of view.

Classroom Organization assesses classroom routines and procedures related to the organization and management of children's behavior, time and attention in the classroom. High-scoring classrooms feature consistent schedules, well-designed learning centers, established routines, and sensitive and appropriate guidance strategies. Staff work together as a team. Classrooms with these characteristics give children a sense of stability and predictability that supports exploring, thinking about, and learning new things.

Instructional Support assesses the ways in which teachers implement the curriculum to effectively promote cognitive and language development. This domain measures how teachers support and extend children's thinking, problem solving and conversational skills, and vocabulary. Effective teachers support children's engagement by making concepts and skills relevant to their everyday lives, asking questions that encourage children to analyze and reason, providing the right amount of help and offering feedback that acknowledges children's attempts.

Yes. While effective interactions are critical and form the foundation for children's school success, they are only one piece of an effective early childhood program. CLASS® does not measure other important components of high quality teaching and learning such as the curriculum used, the process of the ongoing assessment of child progress, or individualized teaching.

Section 641A(c)(2)(F) of the Head Start Act  (the Act) requires that the OHS monitoring review process include the use of ''a valid and reliable research based observational instrument, implemented by qualified individuals with demonstrated reliability, that assesses classroom quality, including assessing multiple dimensions of teacher-child interactions that are linked to positive child development and later achievement.'' The Act also states, in Section 641(c)(1)(D), that such an instrument should be used as part of the system for designation renewal.

ACF consulted with leading early childhood assessment experts prior to selecting the instrument to be used. The experts agreed that CLASS® was the instrument that best met the statutory requirement. Ultimately, ACF selected CLASS®: Pre-K because it is an instrument that has been validated by over 10 years of research in educational settings.

OHS CLASS® reviews are conducted for the purpose of obtaining a grantee-level rather than classroom-level score. To obtain a valid grantee-level score the University of Virginia (UVA) advised OHS to obtain a greater number of observation cycles across classrooms, rather than four cycles at the individual classroom level. Given this, ACF worked with the CLASS® developers to determine the most appropriate number of observation cycles to be conducted. It was determined that two cycles across classrooms would be the most accurate reflection of a grantee-level score.

As a result, and in consultation with the CLASS® developers, the number of observation cycles is two per each classroom observed. This permits the reviewer to conduct observations in more classrooms and so get a grantee-level score.

CLASS®-reliable reviewers are trained and certified as CLASS® observers through Teachstone, the organization that provides training in CLASS®. Teachstone, in collaboration with UVA’s Center for Advanced Study of Teaching and Learning (CASTL) grants certification of all CLASS® observers or reviewers. Reviewers are required to attend a two-day Observation Training provided by a certified CLASS® trainer and then pass a reliability test. This demonstrates that they are reliable with the CLASS®: Pre-K tool and are able to observe teacher-child interactions through the CLASS® lens. Reviewers are required to recertify on an annual basis.

In addition, each review season CLASS® reviewers are provided with professional development that includes activities such as refresher training conducted by a Teachstone trainer, webinars with CLASS® experts, mentor coaching, and access to phone and email support. The quality assurance process includes periodic checks of reliability through a procedure known as calibration, which requires that reviewers code videos alongside another certified observer to ensure that the reviewer remains reliable.

ACF has worked with statisticians to develop a statistically sound methodology for sampling the classrooms in which CLASS® observations will be conducted. The sample of classrooms to be observed is computer generated and randomly drawn based on classroom data entered by the grantee into the Head Start Enterprise System (HSES). This sampling methodology results in a sufficient number of classes being selected from across the grantee to ensure that scores are representative of the grantee.

Once on site the CLASS® reviewer is instructed to make every effort to maintain the original sample of classrooms. In a case where that is not possible, the CLASS® reviewer receives guidance on how to choose a replacement.

Yes. CLASS® reviews are not to be conducted in the first or last two weeks of the program year or during the winter holidays at the end of December. Grantees' classrooms, when the program is beginning and concluding its year or at the end of December, may not be representative of the classroom environment during the program year. Additionally, observations are not conducted during naptime or outdoor unstructured free play.

OHS requires that the CLASS® reviewer be fluent in the predominant language used in the classroom. For example, Spanish language competency is evaluated for CLASS® reviewers who will be assigned to conduct observations in programs and/or classrooms where Spanish is the dominant language spoken by the children. If there is not a reviewer available who is fluent in the language spoken in a classroom, a CLASS® observation is not conducted.

A teacher who has been in the classroom for 10 or more consecutive school days can be observed.

Yes. If the same substitute has been in the class for at least 10 consecutive school days, the class may be observed.

Yes. CLASS® observations can be conducted if the activities are structured and based on a lesson plan. Examples may include a nature walk or organized activities/games played either outside or in a gym area.

In general, each of the two observations conducted in a classroom should be 20-minutes long. There may be instances when an observation cycle is cut short, such as if children leave for unstructured outdoor play or a fire drill occurs. If the observation cycle lasted 10 minutes or more, the observation will be counted.

Yes. Mealtimes are acceptable observation times, regardless of location. If a meal occurs in a cafeteria where other classes who are not being observed are present, the CLASS® reviewer is instructed to get close enough to hear the interactions. If the noise-level in the cafeteria makes it impossible for any interaction to be heard, the class should not be observed.

There are two sets of thresholds for CLASS^® scores in the DRS: the quality thresholds and the competitive thresholds. If a grantee receives a score below the quality threshold for one or more of the CLASS^® domains, OHS provides support for quality improvement by intentionally connecting the grantee to a variety of resources that align with areas where improvement is needed. If a grantee receives a score below the competitive threshold for one or more of the CLASS^® domains, then the grantee is required to compete for continued funding.

The quality thresholds represent OHS's expectation for all grantees regarding the quality of classroom learning environments. These thresholds do not trigger competition; rather, a grantee with a score below a quality threshold receives support from OHS in improving the quality of teacher-child interactions in the classroom. The quality thresholds are as follows: 

• 6 for the Emotional Support domain.
• 6 for the Classroom Organization domain.
• 3 for the Instructional Support domain.

Grantees with average CLASS^® scores below the established competitive threshold on any of the three CLASS® domains is required to compete. The competitive thresholds are as follows: 

• 5 for the Emotional Support domain. 
• 5 for the Classroom Organization domain.
• 2.3 for the Instructional Support domain for CLASS^® reviews conducted through July 31, 2025, and 2.5 for those conducted on or after Aug. 1, 2025.