Over the past decade, Principal Pamela K. Sanders has watched as enrollment at St. Ambrose Catholic School has fallen by more than half. Now she wonders if she'll soon have no school at all.

On Wednesday, the Archdiocese of Baltimore will tell principals, teachers, parents and students about plans to close many of its 64 schools at the end of the academic year and reorganize the system of 22,700 students.

Archbishop Edwin F. O'Brien is taking the steps in the face of rising costs and falling enrollments, problems affecting many of the oldest and largest Catholic school systems in the country.

"We've been praying, the parish has been praying," said Sanders, who has seen the kindergarten to eighth grade at St. Ambrose drop from 330 students when she arrived in 2000 to 160 today. On Wednesday, she said, "at least the uncertainty will be over. So much anxiety comes from the uncertainty."

If the school on Park Heights Avenue, in a neighborhood of boarded-up homes and empty lots, is an extreme case of distress, it still reflects the broader challenges confronting Catholic schools in the traditional urban strongholds of the Midwest, the Mid-Atlantic and New England. The faithful have fled the cities for the suburbs, teaching sisters available to provide instruction at little cost have dwindled in number, and families have been less willing or able to pay rising tuitions.

In Baltimore, archdiocesan officials are attempting to address these problems - which mainly affect the elementary and middle schools - on two fronts. On Wednesday, O'Brien is to detail the plan to close some schools and merge others. He has pledged to offer a space at a new school to every student now enrolled at a school slated to close.

In June, a committee of local education, business and community leaders that O'Brien established a year ago will suggest ways to improve marketing and fundraising, along with other steps meant to keep the system going while sustaining its Catholic character.

The archdiocese, which covers nine counties from Baltimore to Western Maryland, is keeping a tight lid on details of the consolidation plan. Monsignor Bob Hartnett, who headed the group that has been working on the plan since April, said he could not reveal how many students would be affected or even if one part of the archdiocese is going to be affected more than another.

"There's a seat for every child within a reasonable geographic distance of their current school," Hartnett said, defining that distance as no more than five miles, with an average of less than three.

Students have to find their own way to school, as the archdiocese does not provide transportation.

The same guarantee of a spot will not be extended to teachers and administrators, some of whom are going to lose their jobs. Hartnett said school administrators will be told about the plan at a meeting Wednesday morning at the Catholic Center, and children will be given letters that day telling their parents how the plan affects their school.

An announcement to the public will follow on Thursday.

Effie Reynolds is anxiously awaiting word on the fate of St. Ambrose, where her two grandsons attend fourth and first grade. The older boy, Quincy Hairston, has done much better at St. Ambrose than at the public school he left three years ago, Reynolds said.

Like nine of 10 St. Ambrose students, her grandsons are not Catholic. Reynolds was raised as a Baptist and now attends a nondenominational church but said she likes the religious aspect of the school program and the dedication of the staff.

"It's a nurturing environment," Reynolds said. "I don't see public schools as a nurturing environment."

Her family has received aid from the Children's Scholarship Fund, which covers half of the $4,700 tuition for each child. The school is getting by on very little, she said, but "they do compensate for what they don't have" with the attention paid to students.

"I hope and pray they don't close," she said.

While school closings are likely to disrupt family routines, the reorganization could also remove a measure of stability from neighborhoods that sorely need it.

"We truly, truly want to be here," said Sanders, who spent 31 years as a teacher and administrator in Baltimore public schools before joining St. Ambrose. "We know we do such good work in this community."

It was late afternoon. A pair of fifth-graders had closed the school day by reciting the Prayer of Saint Francis - "Lord, make me an instrument of your peace" - over the public address system. Many of the children - the girls in their plaid skirts or jumpers, the boys in their dark blue slacks and dark-blue neckties - were staying for after-school programs. Some students were heading home to a neighborhood that so many others have left behind.

Built in 1926, the pale stone building in the 4500 block of Park Heights Ave. was expanded in the 1950s to accommodate 1,000 students from what was then a thriving working-class area. One nun from the School Sisters of Notre Dame might preside over a classroom of 75 children at a time.

Frank Bramble Sr., the retired Bank of America executive who heads the study committee appointed by O'Brien, attended St. Ambrose from kindergarten through eighth grade in the 1950s and '60s.

If you lived in the neighborhood and were Catholic, Bramble said, it was what you did.

"You just never even considered public school or any other school," said Bramble, who went on to Calvert Hall College High School, also a Catholic school. "It was a different time."

As the 1960s saw historic peaks for Mass attendance and priestly vocations in the United States, so also was the era a high-water mark for Catholic education. In the decades since, the flight to the suburbs has emptied classrooms. The ranks of religious orders have thinned, depriving the schools of teachers who worked for next to nothing, meaning that Catholic schools could no longer be free, or nearly so.

As the bonds of church for many families have loosened, a Catholic education has seemed less essential.

The National Catholic Education Association estimates that about half of Catholic children attended Catholic elementary schools in the 1960s. Today, the figure is about 15 percent.

The recession has deepened the trouble, as families hitting hard times decide they can't afford tuition, which in the Archdiocese of Baltimore can run up to $6,300 a year for elementary school, $10,000 for high school. That is still far less than most other private schools.

Enrollment at archdiocesan elementary and middle schools has fallen from more than 24,000 students during the 2001-2002 school year to 19,000 today. Since 2002, the archdiocese has closed 16 schools.

Early last year, O'Brien said something had to be done in the midst of "what I cannot resist calling a crisis."

The archbishop said schools could not live on tuition alone and had to make new financial arrangements. He said he was open to any proposal, as long as the archdiocese continues to run a school system. That commitment was not negotiable.

The trouble in a word is money. Schools have to figure out ways to raise more of it.

There's a deja vu quality to this, as a strategic study for the schools was conducted by the archdiocese in the late 1980s. Catholic education scholar John J. Convey worked on that plan, which led to new fundraising programs.

Convey, a professor of education at Catholic University of America, an author of several books on the subject, and consultant to several dioceses, detailed a range of possible approaches: new taxes on parishes, greater effort to encourage contributions by parishioners and school alumni, and efforts to build endowments.

When asked the main ingredient for a successful fundraising effort, Convey said, "Get the right leaders in the right place, in terms of pastors and principals."

Since last spring, Bramble said, the 16-member local committee has been studying examples from around the country, and holding meetings throughout the diocese, including sessions devoted to hearing parents and school staff "tell us what's right and wrong with the schools."

He said it was clear from these sessions, and from hundreds of e-mail messages, that parents want Catholic schools not only to sustain their reputation for academic rigor, but to continue to pursue instruction in Catholic religion and values.

The committee's recommendations will surely include that, even if many of the students are not Catholic. Catholic students make up 23 percent of enrollment in Baltimore City, 85 percent elsewhere in the archdiocese.

Bramble and Hartnett said the recommendations that are to be released in June are likely to include stepped-up efforts to promote the schools and affirm ties with alumni.

Hartnett said the archdiocese could do a better job of reminding graduates how much of their success may be due to their Catholic education, whether they are Catholic or not, and how much the schools have yet to offer.

Bramble said he's heartened by the archbishop's commitment to the school system and to staying in Baltimore, and that he remains optimistic.

"The current situation, although challenging, is full of many things to be excited about," he said.