The present study shows how the mixed-methods approach can be used in capturing and organising learning environment (LE) characteristics for the participatory design of psychosocial and physical LEs involving learners. Theoretical constructs were tested and further elaborated on in the analysis of two similar educational design research studies: one conducted with 7- to 14-year-old learners in Finland (n = 80); and the other in Spain (n = 76). Cross-analysis of the numeric, visuospatial and verbal data collected, combined with theoretical and practical considerations, was used to develop a conceptual framework for LE co-design, which draws attention to the importance of balancing communality with individuality, comfort with health, and novelty with conventionality. In line with other studies, in this conceptualisation, flexibility and functionality are seen as central enablers for quality twenty-first century LEs. The knowledge exchange between two countries and the constructs developed in this cross-cultural analysis contribute to the creation of shared content-related design principles for future learning environments.