Once lagging behind other districts in charter school enrollment, Hillsborough County is catching up. • More than 11,000 students were enrolled in these tax-funded but independently run schools last school year. • More are anticipated this year, which is why the district is expanding its administration department to include a director of charter school programs. • Where do the students come from? • District officials recently released a breakdown of the students' original schools. • The numbers vary widely, depending not just on conditions in the neighborhood school but also on the popularity of charters nearby. • Henderson Hammock, a charter school just south of Citrus Park, for example, enrolled 625 students last year, according to state records. Not surprisingly, nearby Cannella Elementary lost 117 and Bellamy Elementary lost 124. • Lutz Preparatory Academy, similarly, had 478 students in a year when nearby Lutz Elementary School lost 105. • District officials track these trends, in part, because when students switch to charters, it affects their operating revenues. By their calculations, charter transfers caused $68 million to leave the district last year.