Teachers and other staffers at the Delaware Valley Charter School, in Logan, voted yesterday to join the American Federation of Teachers in Pennsylvania, union officials said.

The teachers, guidance counselors and school nurses at the school on Old York Road near Wagner Avenue, voted 30-18 to unionize, said AFT organizer Seth Anderson-Oberman.

There are about 50 staffers at the school, he said.

Unless the vote is challenged in the next five days, the Delaware Valley Charter School will be the third charter school in the city to unionize, Anderson-Oberman said. There are 67 charter schools in the city.

Christine Demer, a biology teacher at Delaware Valley Charter, said that the faculty is concerned about job security and a more "transparent" pay scale, and is seeking a stronger voice in the school's operations.

"We have no idea how the salary schedule is derived," Demer said.

She said that the school may be more desperate for teachers in one subject area and would pay a teacher a much higher starting salary than a teacher with equal or higher qualifications in another subject area.

No one from the administration of Delaware Valley Charter School could be reached for comment late yesterday.