Local schools increasingly play a mediating role between intended curricular directives and actual classroom practice. This paper highlights how macro factors such as decentralized governance and subject's institutional status affect school-based decisions to diverge from official curricular policies. Specifically, it reports a three-dimensional comparison from the Israeli education system, i.e. comparing educational levels (elementary and lower-secondary), sectors (Jewish secular, Jewish religious, and Arab), and school subjects (with varying institutional status), to investigate patterns of diversity/uniformity in curricular structures. Between-school variation in curriculum implementation tends to be greater under conditions of increased decentralization and school autonomy. Highly institutionalized subjects are more likely to be taught in conformity with official directives, thereby increasing between-school uniformity. Important political and educational factors have a contextual influence on subject implementation, especially in certain sectors and levels. Ongoing trends toward educational decentralization not only encourage school autonomy, but also heighten curricular diversification. Local schools increasingly determine the educational knowledge students are offered, and effectively enable or constrain what teachers teach. (Contains 6 tables and 25 notes.)