Hackley School is a private college preparatory school located in Tarrytown, New York, and is a member of the Ivy Preparatory School League. Founded in 1899 by a wealthy philanthropist, Frances Hackley, Hackley was intended to be a Unitarian alternative to the mostly Episcopal boarding schools throughout the Northeast. Since its founding, Hackley has dropped its Unitarian affiliations and changed from all-boys to coeducational. Hackley is divided into three schools on the same campus: the Lower School, the Middle School, and the Upper School. Hackley school is also a member of global education association, Round Square.