Millbrook School is a private, coeducational preparatory school located in Dutchess County, New York, USA. It is governed by a self-perpetuating Board of Trustees, and is accredited by the New York State Association of Independent Schools and the Board of Regents of the State University of New York. Institutional memberships include the Cum Laude Society, the Secondary School Admission Test Board, the National Association of Independent Schools, the New York State Association of Independent Schools, the Council for Advancement and Support of Education, and A Better Chance. As of 2009, the school's endowment stood at approximately $20 million; relatively modest in comparison to other private schools in the region.