This thesis provides a historical overview of the development of school libraries up to the present day, exploring their purpose and significance within the education system. As centers of knowledge and resources, libraries play a vital role in supporting both students and teachers, while fostering habits of reading and research. The study examines the mission and operations of school libraries, with a particular focus on the maintenance, supplementation, revision, and withdrawal of library collections. It analyzes current practices in the Republic of Croatia, with special emphasis on statistical data and performance indicators for the region of Istria. Through the review of relevant literature and practical insights, this paper investigates key aspects of school library management and aims to consolidate essential documentation and procedures for implementing protection, revision, and withdrawal processes. The quality of a library's work and the relevance of its collection depend on systematic processes of weeding and upgrading materials. Special attention is given to the importance of regular revisions and withdrawals, which remove outdated or damaged materials, making room for new resources. Moreover, adequate protection measures for library materials are crucial to preserving the cultural and educational value of libraries.