After five months of talks, the Office of Catholic Education and the union representing lay teachers at 17 Catholic high schools remain far apart on terms of a new contract, with the existing agreement expiring Wednesday.

Classes are scheduled to begin Sept. 7. Mary Rochford, the archdiocese's superintendent of schools, said her office hoped the schools would open on time, but said, "We have too many significant issues to resolve" for 16,000 students who attend Catholic high schools operated by the Archdiocese of Philadelphia in the five-county region.

A major obstacle is a preamble the archdiocese wants to include in a new agreement outlining the educational objectives of the high schools.

In addition, the archdiocese wants to overhaul contract language to provide itself with greater flexibility in areas such as teaching assignments and scheduling.

The Office of Catholic Education maintains that the changes are necessary to reflect the altered landscape of 21st-century education. The Association of Catholic Teachers, Local 1776, calls the proposals anti-teacher and antiunion.

Both sides seek to avoid a dispute like the strike in 2003 that kept Catholic high school students out for six days. Contract talks have been scheduled for every day this week.

On Monday, the Office of Catholic Education released a statement saying it was "committed to a contract agreement that respects the needs of not only our teachers but also our school families, who sacrifice to provide a quality Catholic education for their children."

Catholic high school tuition is $5,600 for 2011-12.

Rita Schwartz, the longtime president of the Association of Catholic Teachers, said the issues could be resolved if the Office of Catholic Education expended as much energy at the bargaining table as it did on news releases.

The union representing the 711 lay high school teachers has planned a rally for this morning outside the archdiocese's Center City headquarters in support of the union's negotiating team.

The teachers' association is scheduled to meet Sept. 6 to vote on a new contract.

The contract is the first for Rochford, who was named superintendent three years ago, and she views it as a "hallmark contract." She said a new labor-management agreement was a critical component of the archdiocese's plan to transform its high schools.

"So we are prepared to do what we need to do to make this happen," she said.

Schwartz said Monday: "All the money issues are still on the table, as are these issues that I think are anti-teacher and antiunion. So we have an awful lot of ground to cover in what I think is not a very long period of time."

She said talks were "not going well."

Schwartz said she did not want to negotiate in public by revealing bargaining details. But she said the archdiocese had proposed additions and revisions to every page of the 70-page contract.

"This contract has been in force over 40 years. It has evolved, and it has changed over the years," she said. "If it's not a problem, don't fix it."

Because both sides have spent so much time wrangling over contract language, they have spent little discussing salaries and benefits, the main issues that led to the 2003 strike.

The typical Catholic high school teacher earned $50,550 in the last academic year and has been teaching for 20 years, Schwartz said.

Theresa Ryan-Szott, an administrator in the Office of Catholic Education and the archdiocese's lead negotiator, said the union's initial wage proposal requested salary increases of 22 percent over three years.

"That would simply bankrupt us," she said. "But we have spent very little time on salaries and benefits."

Schwartz said the union's opening request for 22 percent over the life of the contract reflected teachers' responses to a union survey.

"We were following what our teachers said on the contract survey," Schwartz said. "I don't know what we will end up with."