This article presents the research results on developing professional capital in Lithuanian schools during the national project “Time for leaders”. The longitudinal national initiative aimed to develop professional capital as the synergy of human, social and decisional components of schools through educational professionals’ various cooperation-based learning experiences. Using the descriptive case study approach, the article investigates the question of how the cooperative learning approach, applied in a long-term professional development project for education professionals, develop individuals’ professional capital. The paper provides an overview of project interventions (i.e., activities that stimulated cooperative learning of educational professionals) in the light of cooperative learning principles. The assessment of change over two project years in education professionals’ perceptions of professional capital, which is presented using Cohen’s d effect size measure. The measurement sample consisted of teachers (n(I) = 5105; n(II) = 4683) and school leaders (n(I) = 439; n(II) = 405) from 189 schools in 30 Lithuanian municipalities. The findings show a statistically significant medium positive change in professional capital. The most considerable change was estimated in the social and decisional capital dimensions and the relative smallest in the field of human capital.

This article presents the research results on developing professional capital in Lithuanian schools during the national project "Time for leaders". The longitudinal national initiative aimed to develop professional capital as the synergy of human, social and decisional components (Hargreaves and Fullan, 2019) of schools through the various cooperation-based learning experiences of educational professionals. The article provides an overview of project interventions (activities that stimulated cooperative learning of educational professionals) in the light of cooperative learning principles. The assessment of change over two project years in education professionals' perceptions of professional capital is presented using Cohen's d effect size measure. The measurement sample consisted of teachers (n1=5105; n2=4683) and school leaders (n1=439; n2=405) from 189 schools in 30 Lithuanian municipalities. The findings show a statistically significant medium positive change in professional capital. The most considerable change was estimated in the social and decisional capital dimensions and the relatively smallest - in the field of human capital.