Education was critical to William Penn's "Holy Experiment," and in 1689, he had a hand in planting the seed of Quaker schooling in the New World. William Penn Charter School in East Falls and Center City's Friends Select School trace their roots to that seed.

On Thursday night, the two K-12 institutions will join the other 80 Friends schools in 22 states to celebrate the 325th anniversary of Quaker education in America.

And they're marking the milestone in a low-key, Quakerly way. The Friends Council on Education - the umbrella group for Quaker schools across the country - is hosting a gala at the historic Arch Street Meeting House in Old City with a night of reflection, music, and remarks by Jill Biden, the vice president's wife.

"We don't take much time, being a Quaker institution, to stop and have big celebrations, because it's just not what we do," said Darryl J. Ford, who heads Penn Charter and chairs the council. "Quaker institutions are often understated and quietly reserved. I'm very pleased we will take this moment - just this moment - to stop and celebrate 325 years of Quaker education."

The event also will honor Irene McHenry, who will retire from the council this summer after 13 years as executive director.

"I have learned so much about the diversity of Friends education, not only in the United States but around the world," McHenry said Wednesday. "I feel doubly blessed and lucky that my retirement comes when we're celebrating 325 years of Quaker education."

As part of a yearlong observance, Penn Charter is producing a short history of the school, and has begun digitizing documents and artifacts from its archives to illustrate it. Items include a walking stick made from a tree on one of Penn's homesteads, and the charter establishing what was then called "the Philadelphia Friends' Public School."

The school created by Penn existed long before the region had a public school system, and was open to students regardless of religion, income, race, or sex.

"I think the idea is to use different means to bring our history to life," said Ford, a Friends Select graduate. "And quite frankly, I would argue that the history of our Quaker schools and the history of William Penn Charter is the history of the commonwealth."

Randy Granger, an art and design teacher who has been researching the school's archives, said: "We want this stuff accessible to kids and others 300 years from now. . . . We want to make it available to the broadest public and not just to people in Friends schools or Penn Charter."

Friends Select is planning a birthday bash on its campus on the Benjamin Franklin Parkway in September and other events for students.

"What we are doing is more child-centered than anything else," said Rose Hagan, head of Friends Select.

This year, middle-school students from both schools heard storyteller Charlotte Blake Alston recount tales about Penn and Quaker history. And Friends Select has tackled its own history project.

"Part of the celebration will be an archival history telling the history of the United States through the Quaker lens," Hagan said. "It's astounding to think about how old this school is."

Annual tuition at area Quaker day schools can range from $13,000 for preschool to $32,000 for high school, but the schools said they provide financial aid to support the Friends' commitment to diversity.

More than three centuries on, the schools still provide an education centered on principles including simplicity, peace, community, and equality.

Simone Partridge, 22, a Catholic from Wynnefield who graduated from nearby Friends' Central on City Avenue, is a senior at Haverford College, another Quaker institution.

Friends schools, she said, are diverse, welcoming, and democratic, and produce "students who are very reflective and who have a strong voice."