As a social institution, school not only provides learning opportunities but may also give rise to tensions between formal school knowledge and students’ lived experiences. This study aimed to explore upper secondary school students’ perceptions of “existing school knowledge” and “ideal school knowledge” in the city of Tabriz. Adopting a qualitative approach, the study employed thematic analysis based on Braun and Clarke’s framework. The research population consisted of upper secondary school students in Tabriz during the 2022–2025 academic period, who were selected through purposive sampling. Data were collected through 20 individual semi-structured interviews and nine focus-group interviews involving approximately 170 students. The findings revealed that students drew a clear distinction between existing and ideal forms of school knowledge. They generally perceived existing school knowledge as formal, abstract, grade-oriented, memorization-based, and disconnected from their lifeworld. By contrast, they viewed ideal school knowledge as experiential, practical, meaningful, and relevant to real-life issues. The findings further indicated that this gap is not merely educational, but also has cultural and structural roots. Accordingly, rebuilding the connection between school and life requires a shift from a transmission-based model of education toward an interactive, dialogue-oriented, and situated approach—one that can foster critical, meaning-centered, and identity-forming learning in schools.Therefore, existing school knowledge is grounded in instrumental rationality, whereas ideal school knowledge is based on communicative rationality.