How do rival organizational forms that are associated with different ideological values affect each other's growth? And how do ideological polarization and state regulation impact the growth of these rival organizational forms? We adopt a community ecology framework as the stepping-stone to answer these questions in the context of a study of the dynamics of the Turkish high school educational system from 1971 to 1998-a period characterized by important regulatory changes amid growing ideological polarization between religious Islamic and secular factions. We explore how micro-level ideological Islamic-secular polarization and macro-level state regulation as to female participation may impact the meso-level interaction among high school forms. We demonstrate that rival organizational forms affect each other's growth positively, on average, but that this mutualism is reduced by ideological polarization and reinforced by the increase in female participation in Islamic high school education.