For the sixth consecutive year, Philadelphia was the only district in Pennsylvania to have schools on the list, the Philadelphia Inquirer reported.

James Golden, the head of the district safety office, suggested that Philadelphia's accurate reporting is responsible for the number of schools on the list and for the increase, the Philadelphia Daily News said.

"We report, frankly. While I can't speak for other districts, over the last five years, there has been a greater emphasis on reporting crimes," Golden said. "We have always and will continue to emphasize reporting because if we don't know what's going on, we won't know how to respond to it."

Two high schools that were listed last year did not rate as dangerous this year. But five of the 10 schools added to the list were middle schools.

Under the No Child Left Behind act, students can transfer out of persistently dangerous schools. The schools in Philadelphia get additional money for safety.

The rating depends on the number of dangerous incidents relative to a school's enrollment.