This article aims to point out how school autonomy helps principals reach higher quality by increasing flexibility in three areas: pedagogy, organization and management. Autonomy leads to an improvement in student performance and, consequently, in educational quality. A theoretical framework based on literature review and PISA results is followed by a qualitative field study with school management teams in Spain. The study questions how far goes real autonomy in pedagogical, organizational and management issues of the schools. Data from 12 Spanish schools are collected by using a questionnaire made "ad hoc" to assess the three mentioned areas of flexibility. Results show that flexibility for pedagogy, organization and management is very limited in the Spanish schools consulted, coinciding with minimal autonomy granted to these areas by current Spanish legislation on education. The main conclusion reached is that management teams have a key role in promoting autonomy when governments confer it to schools. In accordance with this aim, teacher and management team training is crucial. Broadening the study by data triangulation with other members of the school community (teachers, students and families) is proposed.