Sue Holm has supported Pittsburgh Montessori PreK-8 through seven school years, six principals, three locations and two name changes, while urging Pittsburgh Public Schools officials to make the school more, well, Montessori.

The Squirrel Hill parent will come closer to getting her wish if the Heinz Endowments provides a $247,500 grant to boost the number of Montessori-certified teachers and buy special instructional materials.

"I just think it's a really exciting time for our school now," said Ms. Holm, who has three children there.

With an enrollment of 317, the 26-year-old magnet school, now in Friendship, is one of a relatively small number of public Montessori schools nationwide -- perhaps 350 or more, according to the American Montessori Society. Private Montessori schools number in the thousands.

Supporters said the public schools sometimes struggle to deliver an optimal Montessori experience because of tight budgets, district staffing rules and curriculum constraints spawned by the federal No Child Left Behind Act.

"It's trying to fit an alternative format into a traditional model," lamented Anna Perry, a member of the AMS public policy committee and director of Montessori Education Centers Associated, a teacher-training organization based in Clarendon Hills, Ill.

The philosophy is based on the work of Maria Montessori, an Italian doctor who lived from 1870 to 1952. Montessori programs generally emphasize student inquiry and allow children to work at their own pace, often using beads, cubes or other materials called "manipulatives."

Montessori programs often put students of various ages in the same classroom so that the older children may be role models for the younger. Parents said they like the program, in part, because it promotes social skills.

By Ms. Holm's count, only five of Pittsburgh Montessori's teachers are Montessori-certified. As enrollment has grown over seven school years, she said, officials added a Montessori adviser but no Montessori-certified teachers.

"If we are to have a Montessori program in more than merely name alone, we need to be able to hire Montessori-certified instructors for any openings in our building," Ms. Holm told the school board at a January hearing.

She said staffing rules permit district teachers to bump into positions at Pittsburgh Montessori even if they have no interest in the Montessori program.

West End parent Christine Buffington has had two sons at the school for three years. Devin, 6¹/₂, has had Montessori-certified teachers each year, while Blake, 8¹/₂, never has had one.

"It's unbelievable, the difference," she said, describing Devin as more patient and self-reliant than his brother.

Commitment to the Montessori philosophy varies from school to school, among public and private programs.

"Nobody owns the name 'Montessori,'" said Daisy Klaber, chairwoman of the Greater Pittsburgh Montessori Society and director of Household Harmony, a Mt. Lebanon business that offers family activities. She said society members, including Pittsburgh Montessori, are self-described Montessori schools.

Teacher certification is provided by AMS, Association Montessori Internationale and other groups. But there's "no quality control" at schools, said Dennis Schapiro, publisher and editor of the "Public School Montessorian," a quarterly newspaper in Minneapolis.

Montessori programs pose special challenges to public schools, especially those in financially strapped urban areas.

Mr. Schapiro's paper has chronicled parents' complaints about a lack of Montessori-certified teachers in other cities and the struggle to sustain public Montessori programs, even when they're popular and posting good test scores.

Certification may cost $4,000 to $6,000 per teacher, and equipping a classroom with Montessori materials may cost as much as $25,000, Mr. Schapiro said. He said he fears the No Child Left Behind Act's focus on math and reading has forced some public Montessori schools to say they'll incorporate the Montessori philosophy "every other Tuesday afternoon" and focus on skill drills "until we get test scores up."

"Montessori education isn't designed to move every kid up one grade level every six months," he said.

Ms. Holm and other parents supported Pittsburgh Montessori through a popular principal's death in 2004, a move from one Homewood site to another before the 2004-05 school year, and then a move to Friendship before 2006-07.

The school's name changed from Homewood Montessori to Pittsburgh Montessori to Pittsburgh Montessori PreK-8.

The district said it would spend the Heinz money -- $12,500 for consultants, $160,000 for teacher training and certification, and $75,000 for supplies -- to create a "true" Montessori program.

Parents said they want to emulate successful public programs in other districts, including the Springfield Public Schools in Massachusetts.

Josh Bogin, Springfield director of magnet schools, said Zanetti Montessori Magnet School is so popular it has had 200 to 300 students on a waiting list. He said the district last fall opened a second Montessori school, in part because of Zanetti's track record.

Since Zanetti became a Montessori school in 1999, academics and discipline have improved. But Mr. Bogin said he isn't sure whether the gains are attributable to the Montessori approach, which included use of a federal grant to certify teachers; to the families attracted to the school; or both.