Khepera Charter School teachers, who just last month were so frustrated by 18 months of contract talks that they gave negotiators the power to call a strike, ratified a new contract Monday.

The 24-member local that represents teachers and counselors at the Mount Airy charter, unanimously approved a three-year pact that includes retroactive pay raises of 2 percent to 4 percent in two of the three years and maintains a defined salary schedule.

"I want to thank everyone who supported us, including . . . parents and the community," said Kim Johnson, the president of the Alliance of Charter School Employees, Local 6056. "It was long, but it was worth it. Now we can focus 100 percent of our attention on the students."

Johnson, a science teacher who also served on the negotiating team, said the new contract would help stem teacher turnovers at the K-8 school.

Richard Isaac, Khepera's board president, could not be reached for comment.

The new pact replaces a contract that expired in December 2012 and was extended three times. Union members were so fed up with Khepera's board that they unanimously gave their negotiators the power to call a strike.

None of the handful of charter schools in Pennsylvania that are unionized has ever staged a walk out.

Khepera's new agreement encourages professional growth and development of the teachers by creating a professional leave program with a revised tuition-reimbursement program. The contract establishes a labor-management committee to promote communication and collaboration, and a teacher-evaluation process with feedback.

Khepera, which opened in 2004, enrolls 444 students on two campuses, 6641 Ardleigh St. and 144 W. Carpenter Lane.

The school's five-year charter is up for renewal, and the district's charter office is reviewing Khepera's operations. 215-854-2789