This article explores School Participatory Budgeting (SPB) as an important practice that provides students with opportunities to show their agency, or the ability to proactively influence social structures and institutions. The study explores the manifestations of agency among schoolchildren involved in SPB. The empirical base of the study includes the results of a survey of 670 students in grades 7-11, conducted from May to October 2023 in 32 regions of Russia. The survey contained questions about the specific practices in which schoolchildren participated. The level of agency was determined using a specially developed methodology that allows for the assessment of students’ agency in various fields, such as family, education process, school life, interaction with peers, and income. The results showed that schoolchildren’s level of agency is closely related to their involvement in SPB. The higher the level of agency, the higher the level of involvement in SPB. A high level of agency and the maximum degree of involvement are only typical for a small percentage of respondents. The main motives for schoolchildren’s participation in SPB are personal development, the acquisition of new skills and knowledge, and social mobility. Participants in SPB with the highest level of agency often seek changes in existing practices and regulations and the implementation of socially significant projects aimed at improving the life of the school community.