Jacksonville is organized under the city charter and provides for a "strong" mayor–council form of city government. The Mayor of Jacksonville is elected to four-year terms and serves as the head of the government's executive branch. The Jacksonville City Council comprises nineteen members, fourteen representing single-member electoral districts of roughly equal populations, and five elected for at-large seats. The mayor oversees most city departments, though some are independent or quasi-independent. Law enforcement is provided by the Jacksonville Sheriff's Office, headed by an elected sheriff; public schools are overseen by Duval County Public Schools, and several services are provided by largely independent authorities. The mayor holds veto power over all resolutions and ordinances made by the city council and also has the power to hire and fire the head of various city departments.