Leaders of Anne Arundel's first charter school say they have cleared the last bureaucratic obstacle to opening next month in Annapolis.

The KIPP Harbor Academy and the Anne Arundel teachers union reached a tentative agreement Tuesday that they believe will win approval from the county school board, which dealt the charter school a major setback last week when it voted down an earlier version of the compact.

Classes are set to begin in mid-July at the Knowledge Is Power Program school, the first charter campus to open in the county under a new state law that encourages the privately run public schools. KIPP is a nationwide charter and alternative school organization that has won acclaim for raising achievement among low-income minority students.

KIPP spokesman Steve Mancini said the agreement means there are "absolutely no objections to KIPP Harbor Academy opening." He added, "We're very appreciative to the union to be willing to do this."

KIPP's entrance to Anne Arundel has been an ongoing drama. The local school board first denied the school's application, then swiftly changed its mind after word spread of KIPP's national reputation as a performance magnet for urban black and Hispanic children. At several points since, the fate of KIPP has seemed in doubt. Last week, the Anne Arundel school board denied an agreement worked out between KIPP and the teachers union, a document that was considered essential to the school's proper functioning.

School board members rejected the agreement between KIPP and the Teachers Association of Anne Arundel County because of two proposed amendments that are not part of the contract that governs other Anne Arundel teachers. One is a concept called "fair share" -- wanted by the union -- which calls for KIPP teachers who do not belong to the union to pay an amount equivalent to dues. The other is an unusual arbitration process that gives KIPP considerable autonomy in dealing with labor issues.

The arbitration clause was seen as important by KIPP to its charter education philosophy of operating well outside the school system bureaucracy in exchange for a promise to deliver adequate performance.

On Tuesday, the charter school and teachers union decided to drop the two divisive items. Dues and arbitration will be handled in the same way they are handled at all other Anne Arundel schools. The agreement will be sent back to the school board July 6 in modified form, Mancini said. The goal is to have a labor agreement in place before the regular academic year begins in the fall.

KIPP leaders say the school can open even without the labor agreement, although school system administrators don't entirely agree. Without the signed agreement, KIPP's success may hinge on teachers agreeing to work extra hours without a formal contract to enforce their schedule. KIPP teachers will be paid about 20 percent more than the normal union scale because of their extended work hours.

An extended work week is required of KIPP teachers, a departure from the schedule for the rest of the county's teachers. The rigorous KIPP model requires teachers to hold classes from 7:30 a.m. to 5 p.m. daily and on alternate Saturdays, along with a four-week summer session. Teachers must also carry cell phones and be ready to answer calls from students and parents at home.

"What's motivating teachers to work at KIPP is not legal requirements, but a desire to send kids to college," Mancini said.

Leaders of the 75,000-student Anne Arundel school system worried KIPP might not be able to open without a special amendment to the labor contract governing the county's 5,000 teachers.

If KIPP cannot open in the fall, there is fear of a last-minute scramble to find seats for KIPP students in other Anne Arundel schools, said Jose Torres, an assistant superintendent who oversees charter schools. KIPP is recruiting a first-year class of about 80 fifth-graders, primarily from the Annapolis area.

As the uncertainty played out over the past week, KIPP administrators did their best to reassure prospective students and their parents that the school will open as expected. Legally, the school board cannot prevent the school from opening as long as all rules are followed. KIPP leaders say they have been through this sort of thing before in other jurisdictions that have struggled to understand the ins and outs of charter education.