For the first time since Catholic high school teachers in the Archdiocese of Philadelphia went on strike last week, there will be no school for any of the 16,000 students beginning Wednesday and until a settlement is reached and striking teachers return.

And the archdiocese rejected an offer Tuesday evening by the Association of Catholic Teachers, Local 1776, that could have allowed students to return to class.

The union had offered to send its teachers back to work at the 17 high schools - if the archdiocese agreed to bring in a mediator to help resolve the labor dispute.

The archdiocese, which had twice rejected the union's request for a mediator, said that its position had not changed "because of the unique issues facing Catholic schools," the Office of Catholic Education said. "We are willing to work around the clock to provide our students and school families with the best educational environment possible. Discussions over the past two days have been productive. With the parties who best understand these issues remaining at the table and continuing to make progress, we can accomplish our goal."

The mediation discussion was triggered by a letter Patrick J. Eiding, president of the Philadelphia Council of the AFL-CIO, sent to both sides. If mediation was accepted, Eiding said he would urge teachers to return to their classrooms under provisions of the contract that expired Aug. 31 while talks continued.

Rita Schwartz, president of the teachers' union, told reporters that she thought Eiding's suggestion was a good one.

"I'm willing to try it to get this done," she said, hours before the archdiocese announced its decision. "If the archdiocese is not, that's on them then, if they want to keep the schools closed when they have an opportunity to open them."

Schwartz said she had hoped the union's willingness to return to school while talks continued might persuade the Office of Catholic Education to alter its stance.

She said later: "They are unwilling to consider mediation and our teachers' return to the classroom. Unfortunately, this means that the schools will remain closed."

Talks were scheduled to continue Wednesday and Thursday.

Teachers have been manning picket lines outside their schools in two shifts between 7 a.m. and 1 p.m.

Although the 711 lay teachers have been on strike since they rejected the archdiocese's contract proposal Sept. 6, students began returning to school last week for staggered orientation and testing sessions with administrators and members of religious orders providing staffing.

But realizing it would be difficult to provide classroom instruction, the Office of Catholic Education decided to close the high schools.

"We are not able to bring the entire school population back into the building with reduced staffs since this would compromise the safety of the school and our students," officials said in a letter to parents.

The Philadelphia Catholic League athletic programs, however, will continue with their planned schedules.

The teachers' union and the archdiocese began bargaining in March to try to craft a new labor agreement. They have been at odds over the archdiocese's desire to overhaul the contract to reflect what it sees as the altered educational landscape of the 21st century, and to give it greater flexibility and control over teaching assignments and scheduling.

Striking teachers have said they objected to proposed changes in working conditions and were concerned about job security and the archdiocese's intent to use more part-time instructors.

A two-week strike in 2003 over wages and health benefits kept students out of archdiocesan high schools for six days. Students made up the time on holidays and holy days.

The current labor dispute does not affect students who attend Catholic elementary schools, whose teachers are not unionized.