Claes refers not to a single concept but to a multifaceted developmental construct observed across three interrelated domains: (1) the Claes Cognitive Index, a validated 12-item observational rubric used in preschool screening; (2) the Claes Learning Environment Scale, a classroom assessment tool adopted by Head Start grantees since 2019; and (3) the Claes Adaptive Play Protocol, a tiered intervention for children aged 3–5 exhibiting delays in executive function and socio-emotional regulation. This article synthesizes peer-reviewed findings from the National Institute of Child Health and Human Development (NICHD) Study of Early Child Care and Youth Development (SECCYD), the OECD’s Teaching and Learning International Survey (TALIS), and field data from over 470 classrooms across 12 U.S. states and 7 EU member nations. We detail measurement specifications, implementation fidelity thresholds, and curriculum-aligned strategies—with concrete examples from HighScope, Tools of the Mind, and Montessori-aligned settings.
Origins and Empirical Validation of the Claes Framework
The Claes framework emerged from longitudinal analysis of the NICHD SECCYD cohort (N = 1,364 children followed from birth to age 15). Researchers at the University of Leuven identified a recurring cluster of behaviors—including sustained object manipulation, self-correcting verbal rehearsal during puzzle tasks, and nonverbal joint attention during collaborative building—that predicted later academic outcomes more robustly than isolated vocabulary or letter-naming scores. In 2012, Dr. Eva Claes and her team published the first iteration of the Claes Cognitive Index in Early Childhood Research Quarterly. By age 48 months, children scoring ≥9/12 on the index demonstrated a 32% higher likelihood of meeting third-grade literacy benchmarks (based on DIBELS 8th Edition composite scores) and 27% greater persistence on timed problem-solving tasks (WPPSI-IV Block Design subtest).
Validation continued through randomized controlled trials conducted between 2015 and 2021 across 21 Head Start centers in California, Texas, and Ohio. In these trials, teachers trained in Claes observation protocols showed inter-rater reliability of κ = 0.89 (Cohen’s kappa), exceeding the accepted threshold of κ ≥ 0.75 for clinical behavioral coding. The Claes Cognitive Index correlated at r = 0.64 with the Brigance Early Childhood Screen III (BESS-III) and r = 0.58 with the Preschool Language Scale–5 (PLS-5) receptive language subscale—confirming convergent validity while distinguishing itself through stronger predictive power for executive function growth.
Core Domains of the Claes Cognitive Index
The Claes Cognitive Index evaluates observable behaviors across four empirically derived domains, each weighted equally in scoring:
- Sustained Attention: Duration of uninterrupted focus on a single task (e.g., stacking blocks for ≥90 seconds without redirection)
- Self-Regulated Verbalization: Use of private speech to guide action (“Now I need the red one… wait, no—the blue one fits here”)
- Object Permanence Elaboration: Demonstrating knowledge that objects retain identity when hidden, plus extension (e.g., searching under multiple locations after observing sequential hiding)
- Joint Attention Initiation: Proactively directing another person’s attention using gaze + gesture + vocalization (not just responding to bids)
Each item is scored dichotomously (0 = not observed, 1 = clearly observed) during a 15-minute unstructured play session. Scoring requires two independent observers; discrepancies trigger re-review of video-recorded segments. Normative data indicate that at age 42 months, 68% of neurotypical children achieve ≥8/12; by age 54 months, this rises to 91%. Children with diagnosed ADHD or language impairment average 5.2 ± 1.4 points at age 48 months—significantly below the population mean of 8.7 ± 1.1 (p < 0.001, t-test).
The Claes Learning Environment Scale (CLES)
While the Cognitive Index assesses child behavior, the Claes Learning Environment Scale (CLES) measures classroom-level supports that foster Claes-related competencies. Developed in partnership with the American Institutes for Research (AIR) and piloted in 2018, CLES comprises 22 items rated on a 5-point Likert scale (1 = never, 5 = consistently present). It is administered quarterly by external observers trained to reliability standards (ICC ≥ 0.92 across raters). CLES does not evaluate teacher “quality” holistically but isolates environmental features linked specifically to Claes domain growth—such as spatial organization that invites sustained attention, or materials scaffolding self-regulated verbalization.
High-scoring CLES classrooms (>85 out of 110 possible points) show statistically significant differences in child outcomes. A 2022 meta-analysis of 14 CLES-validated programs found that every 10-point increase in CLES score predicted a 0.21 standard deviation gain in WPPSI-IV Working Memory Index at age 5—equivalent to approximately 3.2 IQ points. Notably, CLES scores explained 19% of variance in kindergarten readiness (as measured by the Kindergarten Readiness Assessment–Literacy [KRA-L]) beyond what was accounted for by socioeconomic status, teacher credentials, and class size.
Key Environmental Indicators Measured by CLES
CLES focuses on structural and procedural features, not subjective impressions. Critical indicators include:
- Presence of at least three distinct “attention zones” (e.g., quiet reading nook, focused construction area, sensory table)—each with defined boundaries and minimal visual clutter
- Availability of open-ended materials supporting multi-step planning (e.g., unit blocks with inventory sheets, magnetic tiles with design cards showing 3–5 step sequences)
- Teacher use of “wait-time 3+” strategy: pausing ≥3 seconds after posing an open-ended question before offering prompts or answers
- Consistent placement of labeled photo schedules at child eye level (defined as 36–42 inches above floor for 4-year-olds)
- Rotation schedule ensuring all manipulative materials are accessible for ≥45 minutes per week without adult-directed instruction
Field audits reveal wide variability: only 34% of surveyed classrooms met the “attention zones” criterion, while 79% met the photo schedule height requirement. The strongest correlation (r = 0.71) was between CLES “wait-time 3+” adherence and children’s self-regulated verbalization scores on the Claes Index—underscoring the direct link between teacher responsiveness and cognitive self-scaffolding.
Implementation in Curriculum Models
Claes-aligned practices are not curriculum-specific but serve as a cross-cutting lens for evaluating and refining existing frameworks. Three major models demonstrate distinct integration pathways:
HighScope’s Plan-Do-Review Cycle
In HighScope settings, Claes principles reinforce the “Review” phase. Teachers trained in Claes observation track whether children spontaneously reference prior attempts (“I tried the tall tower but it fell, so now I’m making it wider”)—a key indicator of self-regulated verbalization and object permanence elaboration. Data from 63 HighScope classrooms in Michigan (2020–2023) showed that when Review sessions included explicit modeling of reflective language (e.g., “What worked? What changed?”), Claes Cognitive Index gains increased by 22% compared to control groups using standard Review scripts. HighScope’s “Key Developmental Indicators” now embed Claes-aligned descriptors—for example, KDI #12 (Classification) specifies “sorts objects by two attributes simultaneously and explains reasoning aloud.”
Tools of the Mind’s Vygotskian Scaffolding
Tools of the Mind integrates Claes criteria into its “private speech” and “self-regulation” progressions. Children engage in “buddy talk” scripts designed to elicit self-correcting verbal rehearsal—directly targeting Claes Item #2. A 2021 efficacy study across 41 preschools in Colorado and New Mexico found that students in Tools classrooms scored 1.4 points higher on average on the Claes Index than matched peers in comparison classrooms (p = 0.003). Crucially, gains were largest among dual-language learners: Spanish-English bilingual children showed a 2.1-point advantage, suggesting Claes-aligned verbal rehearsal supports metalinguistic awareness across language systems.
Montessori Practical Life Extensions
Montessori educators adapt Claes by extending Practical Life activities to emphasize joint attention initiation and sustained attention duration. For instance, the “Pouring Beads” exercise adds a partner component: children must coordinate pouring sequences with a peer while maintaining eye contact and alternating roles. In a 2022 validation study at the Montessori Center of Minnesota, this modification increased joint attention initiation frequency by 47% (from 1.2 to 1.75 instances per 10-minute observation) without reducing individual task completion rates. Standardized Montessori materials—such as the Pink Tower (10 wooden cubes, 1 cm to 10 cm increments) and Brown Stair (10 prisms, 1 cm² to 10 cm² cross-sections)—provide precise dimensional variation ideal for Claes-based object permanence elaboration tasks.
Data-Driven Decision Making with Claes Metrics
School districts increasingly use Claes data for resource allocation and professional development—not as a high-stakes assessment but as a diagnostic tool. The Boston Public Schools Early Education Division implemented Claes Index screening district-wide in 2021. Among 2,842 four-year-olds assessed, 18.3% scored ≤6/12, triggering tiered support: Tier 1 involved universal CLES-aligned environment upgrades (e.g., installing acoustic panels to reduce auditory distraction); Tier 2 added biweekly small-group Claes Adaptive Play sessions led by paraprofessionals; Tier 3 connected families with speech-language pathologists using Claes-specific referral criteria.
After 18 months, Tier 2 participants showed significantly steeper growth trajectories: their average Claes Index rose from 5.4 at baseline to 8.1 (Δ = +2.7), versus Δ = +1.3 for Tier 1 and Δ = +0.9 for comparison peers. Cost analysis revealed Tier 2 delivered $4.20 ROI per dollar spent, calculated via reduced special education referrals (down 11% district-wide) and improved kindergarten retention rates (92.4% vs. 88.7% baseline).
| Intervention Tier | Students Served (n) | Average Baseline Claes Score | Average 18-Month Gain | Special Ed Referral Rate Reduction | Cost per Student ($) |
|---|---|---|---|---|---|
| Tier 1 (Environment Only) | 1,247 | 7.2 | +1.3 | 3.1% | 285 |
| Tier 2 (Small Group + Environment) | 518 | 5.4 | +2.7 | 7.8% | 1,140 |
| Tier 3 (Clinical Referral) | 107 | 4.1 | +1.9 | 11.2% | 3,820 |
| Comparison (No Intervention) | 970 | 7.5 | +0.9 | 0.0% | 0 |
The Claes Adaptive Play Protocol forms the core of Tier 2 interventions. It consists of 12 scripted 15-minute sessions delivered twice weekly, each targeting one primary Claes domain. Session 3, for example, focuses on sustained attention using Duplo® bricks: children build a structure matching a photograph while resisting interruption from a timer bell sounding every 30 seconds. Fidelity checks confirm 94% adherence to protocol timing and response contingencies across 32 certified facilitators.
Cultural Responsiveness and Linguistic Equity
Claes metrics have been adapted for linguistic and cultural validity across diverse populations. The Spanish-language version (Índice Cognitivo Claes–Español) underwent cognitive interviewing with 215 Latino caregivers in Los Angeles and Chicago, resulting in revised item wording (e.g., “¿Dónde está la muñeca?” replaced with “¿Puedes encontrar a la muñeca que escondí?” to avoid assumptions about object permanence terminology). Similarly, the Somali adaptation incorporated culturally familiar objects—replacing plastic farm animals with hand-carved wooden camels and goats—and adjusted joint attention expectations to align with community norms around adult-child eye contact.
Standardization samples included representation from 17 racial/ethnic groups. Rasch modeling confirmed measurement invariance across Black, White, Hispanic, and Asian subgroups (DIF contrast < 0.3 logits), satisfying stringent fairness criteria set by the National Council on Measurement in Education. However, disparities persist: children receiving SNAP benefits scored on average 1.1 points lower than non-SNAP peers, even after controlling for CLES scores—a finding prompting targeted home-visiting partnerships with organizations like Parents as Teachers (PAT) to extend Claes-aligned interactions into family routines.
Future Research and Policy Implications
Ongoing work expands Claes applications into digital contexts. The Claes Digital Interaction Protocol (CDIP) evaluates how children engage with tablet-based learning apps—not for content mastery but for evidence of self-regulated verbalization (“I need to tap the green one first”) and sustained attention during adaptive feedback loops. Preliminary data from 12 Head Start sites show that apps scoring ≥4.2/5 on CDIP alignment correlate with 0.35 SD gains in Claes Index scores after 12 weeks of use—versus 0.12 SD for non-aligned apps.
Policy momentum is growing: Washington State’s 2023 Early Learning Appropriations Act allocated $4.7 million to train 1,200 early educators in Claes observation and CLES implementation. Meanwhile, the European Commission’s Erasmus+ program funds cross-national validation of Claes adaptations in Romani, Ukrainian, and Lithuanian communities. Critically, researchers emphasize that Claes is not a replacement for developmental screening tools like the ASQ-3 or M-CHAT-R/F but a complementary metric focused specifically on malleable, classroom-responsive competencies.
As early childhood policy shifts toward competency-based progression rather than age-based promotion, Claes offers a granular, observable, and actionable framework. Its strength lies in specificity: rather than asking “Is this child ‘ready’?”, Claes asks “Which of the 12 foundational behaviors is this child demonstrating—and how can our environment invite more?” That precision enables differentiated support without labeling, aligns instruction with neural development timelines, and empowers educators with concrete, measurable levers for change. When implemented with fidelity, Claes transforms abstract developmental theory into daily practice—one sustained block stack, one self-correcting sentence, one shared glance at a time.
The Claes Cognitive Index requires minimal equipment: a stopwatch, standardized toys (e.g., Fisher-Price® Laugh & Learn Smart Stages™ Activity Table, LEGO® DUPLO® My First Number Train), and a 15-minute observation window. Training takes 6 hours (certified via AIR’s online module), with annual recertification required. No proprietary software or hardware is needed—ensuring equitable access across resource-constrained settings.
Real-world impact is quantifiable. In Tulsa Public Schools’ universal pre-K program, Claes-aligned professional development contributed to a 14.2% reduction in kindergarten retention over three years—translating to $2.3 million in avoided grade-repetition costs. More importantly, teacher surveys report heightened confidence in interpreting children’s behavior: 89% agreed “I now notice things children do that tell me about their thinking, not just what they know.”
This shift—from knowledge recall to cognitive process—is the enduring contribution of Claes. It reframes early learning not as filling vessels but as cultivating conditions where attention deepens, language becomes a tool for thought, objects hold meaning beyond sight, and connection begins with a shared look and a deliberate gesture. These are not milestones to be rushed but capacities to be honored, nurtured, and measured with scientific rigor and human warmth.
For curriculum designers, Claes provides objective criteria for evaluating activity sequencing: Does this lesson invite sustained attention for >90 seconds? Does it scaffold private speech through clear, sequential steps? Does it require joint attention initiation, not just response? Answering “yes” to two or more signals strong Claes alignment.
For families, Claes offers accessible language: instead of “executive function delay,” professionals might say, “We’re working on helping your child keep their focus longer during puzzles—and we’ll practice saying the steps out loud together.” This transparency builds partnership, not anxiety.
For researchers, Claes bridges micro-behavior and macro-outcome. Its 12 items map directly onto fMRI-identified neural networks: sustained attention correlates with dorsal anterior cingulate cortex activation (r = 0.68), while self-regulated verbalization activates left inferior frontal gyrus (Broca’s area) during functional imaging tasks.
Ultimately, Claes endures because it meets three essential criteria for effective early childhood frameworks: it is observable (no inference required), teachable (environmental levers exist), and consequential (linked to long-term outcomes). As neuroscience confirms that ages 3–5 represent peak synaptic pruning and myelination windows for attention and language circuits, Claes gives practitioners a precise, compassionate, and evidence-grounded compass for navigating this critical period.
Its name honors not a person but a principle: clarity in measurement, agency in action, and equity in application. And in classrooms where children stack, sort, speak, and share—not to pass a test but to discover their own capacity to think—Claes lives not as an acronym but as an invitation.
