The present study offers a theoretical and methodological rationale for establishing a collaborative environment - referred to as a “third space”- between secondary schools and higher education institutions. This environment is intended to stimulate and enhance students’ research and inquiry-based activities by engaging them in joint scientific projects with academic mentors, supervisors, consultants, and reviewers. The article conceptualizes the notion of “third space,” delineating its defining properties, types, and formats in the context of productive school–university cooperation aimed at implementing research-oriented educational projects. Within the framework of this study, the “third space” is understood as a hybrid, flexible, and innovation-driven environment that integrates the resources and capacities of both schools and universities to support the development of student research. Its key characteristics are identified as openness, informality, collaboration-orientation, co-creation of research, and systematic exchange of knowledge and experience. The authors argue that joint research activity within such a space is becoming increasingly essential due to the growing societal demand for competitive graduates equipped with collaboration skills, research competencies, intrinsic motivation for disciplinary learning, and the ability to navigate future career paths. As a practical solution for ensuring the functioning and organization of the “third space,” the study substantiates the creation of a digital platform that serves as an effective environment for collaborative project development in the field of Digital Humanities. The article outlines the core functions of the platform, describes its collaborative structure (students, supervisors, tutors, reviewers), and demonstrates its effectiveness in supporting school-based research projects through a three-level system of scientific and methodological guidance. The findings of the study may be useful for school and university administrators seeking to design and implement effective forms of cooperation aimed at improving joint research activities and fostering a sustainable school–university partnership.