Background/Objectives: Motor competence is a multidimensional indicator of developmental health, yet most studies treat it as a single composite outcome and ignore the contextual class-level structure of school-based data. This cross-sectional study examined motor competence across three domains, manual dexterity, aiming-catching, and balance, in 312 Greek primary school children aged 6–12 years (156 girls) using the Movement Assessment Battery for Children–Second Edition (MABC-2). Methods: Standard scores were analyzed using a linear mixed-effects model with correlated domain-specific random slopes at both the class and student levels, partitioning inter-individual variability in overall motor level, intra-individual variability in domain profiles, and contextual class-level contributions. Post-hoc power analysis via parametric bootstrap confirmed adequate power for the primary outcome and indicated that non-significant age and sex main effects were negligibly small rather than undetected. Results: Balance yielded the highest standard scores, followed by aiming-catching and manual dexterity, with all three domains differing significantly. Neither age nor sex produced significant main effects. A significant component × sex interaction revealed domain-specific sex differences: boys outperformed girls on aiming-catching, while balance exceeded aiming-catching among girls but not boys. However, the observed interaction effect fell below the minimum detectable effect size threshold, suggesting potential upward bias and warranting cautious interpretation pending replication in larger samples. Approximately 13% of children were classified as at risk and 9% showed scores consistent with severe coordination difficulties. Contextual class-level sources accounted for 23.4% of total variance, with 52% of classes deviating significantly from the population mean. Conclusions: These findings highlight manual dexterity as a curricular priority in Greek primary physical education and underscore the importance of contextually sensitive, domain-specific approaches to motor competence monitoring and intervention.

Background/Objectives: Motor competence is a key indicator of children’s developmental readiness and an important component of health and well-being education. It is conceptualized as a latent construct shaped by both individual and contextual factors. The objective of this study was to examine the influence of sex, age and class context on motor competence, with particular emphasis on skill-specific and contextual variability. Methods: Motor competence was assessed in 312 Greek primary school children aged 6–12 years (156 girls) using the Movement Assessment Battery for Children–Second Edition. Standard scores for manual dexterity, aiming–catching, and balance were analyzed using a multilevel modeling approach. Results: Balance showed the highest standard scores, while manual dexterity was the lowest-performing domain. Boys outperformed girls in aiming–catching, with a modest effect. Age effects were domain-specific, with relative age within the classroom negatively associated with manual dexterity but not with other domains. Class-level factors explained substantial variance, indicating heterogeneity across classes. Conclusions: Motor competence in primary school children is strongly domain-specific and meaningfully associated with classroom context. Manual dexterity emerges as a potential priority for curriculum development, and age-related effects appear to operate selectively across domains.