Upper Darby School District (UDSD) is a large public school district of approximately 12,000 students in Upper Darby Township, Delaware County, Pennsylvania. It consists of an 8.3-square-mile (21 km2) area including Upper Darby Township, Clifton Heights borough, and Millbourne borough. According to 2009 local census data, it serves a resident population of 90,000. In 2009, the district residents’ per capita income was $20,699, while the median family income was $51,965. In the Commonwealth, the median family income was $49,501 and the United States median family income was $49,445, in 2010. According to District officials, in school year 2007–08, Upper Darby School District provided basic educational services to 11,700 pupils.