Introduction. The transformation of the student into a genuine agent − both of cognitive activity and of everyday life – is viewed as the primary guiding principle of modern primary education. It is during this developmental stage that the fundamental personal mechanisms of volitional control, goal-setting, self-organization, and reflective self-awareness begin to emerge. The purpose of the study: to theoretically substantiate, develop, and experimentally verify a comprehensive set of external and internal psycho-pedagogical conditions that foster the effective development of primary school children's agency. Materialsand methods. The study involved 364 participants: 196 primary school students in years 1-4 (111 girls and 85 boys), eight primary school teachers and 160 parents. The experimental and control groups each comprised 50 pupils in years 3 and 4 (Center of Education №1, Belgorod). The diagnostic toolkit encompassed the Child Agency Assessment Technique (N.I. Vyunova, N.A. Zhestkova), Volitional Self-Assessment and Imaginary Situations tests (M.V. Matyukhina, S.G. Yarikova), the modified “Who Am I?” technique (M. Kuhn), Teacher Agency Questionnaire (E.N. Volkova, I.A. Seregina), STOP Pedagogical Communication Style inventory, parental questionnaires, and teacher expert evaluation forms. Statistical data processing was executed in SPSS using Kruskal-Wallis, Mann-Whitney U, Wilcoxon T, Fisher's φ* transformation, and Spearman's rank correlation. Results. Structural and gender-specific peculiarities of agency were identified: girls demonstrated significantly higher levels of agency towards themselves (U_emp = 3670, p≤0.01), towards others (U_emp = 3762, p≤0.01), and integrated agency (U_emp = 3639, p≤0.01). A substantial divergence between children's self-assessed autonomy and teachers' expert assessments was documented (T_emp = -12.07, p≤0.01). A 12-session developmental intervention targeting students and an educational module for teachers and parents were implemented. A postintervention assessment revealed statistically significant improvements across all agency dimensions in the experimental group (p≤0.01). Conclusions. The findings substantiate that the emergence of agency is contingent upon the synergistic unity of internal personal resources (self-worth, reflection, internal action plan) and external environmental mediation.