This chapter explores the influence of school organizational factors on effective education for sustainable development (ESD) within primary schools, emphasizing the whole school approach (WSA) as a key enabler of sustainable change. Utilizing secondary data from the Trends in International Mathematics and Science Study (TIMSS) 2023 cycle, covering 28 education systems, this research explores cross-national variations in fourth-grade students’ environmental knowledge and attitudes. Particular attention is given to the relationship between school-level organizational characteristics, as outlined in the ESD-effective school framework, and students’ environmental knowledge and attitudes. Findings reveal significant system-level differences in knowledge and attitudes, alongside an unexpected, weak negative correlation between these two dimensions. Urban–rural disparities are also evident, particularly in Eastern Europe, where urban students often show higher environmental knowledge, while some rural areas exhibit stronger environmental attitudes. Notably, school emphasis on sustainability and resource availability demonstrate limited, primarily weak positive associations with both knowledge and attitudes. The chapter concludes by discussing the implications of these findings for restructuring school organizational practices to align with sustainability education policies, such as Sustainable Development Goal 4 and the GreenComp framework, and calls for future assessments to better capture the holistic and process-oriented nature of WSA.