It was just an old, dust-covered painting of a long-forgotten school principal, or so the maintenance man thought. It had been sitting next to the boiler in the storeroom for a long time -- too dank to hang, but a bit too pretty to throw out.

Fortunately, no one ever did ditch the portrait, for it was done by renowned painter Thomas Eakins in 1902 of John Seely Hart, a former principal of Central High School in Philadelphia, for the dedication of a new school building that year. Eakins, who had grown up and attended schools in Philadelphia, was commissioned to do the portrait by a school alumnus, and it hung in the school for a time before being relegated to storage.

Now that portrait is among a treasure trove of art discovered in Philadelphia schools -- as much as $30 million worth. The school district had commissioned a survey of school buildings over the past year to see what art existed. It expected to find a few interesting pieces in odd places, but nothing like this.

"There may be as many as 100 museum-quality pieces in the Philadelphia schools' collection, and that is pretty amazing," said Kathleen Bernhardt-Hidvegi, a Chicago-based art consultant who supervised the cataloging of the Philadelphia school art, about 1,200 pieces. She said the Eakins portrait of Hart alone may be worth as much as $600,000. "Perhaps not in the recent history of art has anyone discovered so much at once so valuable. You hear of the random Monet in an attic, but nothing like this."

The Philadelphia School District chief of staff, Natalye Paquin, and district chief executive Paul Vallas did a similar survey when they worked together in Chicago in the mid-1990s.

"A parent saw a painting he liked on a school wall and put in a six-figure bid for it," Bernhardt-Hidvegi said. "Someone in the legal department said, 'Wait a second. We must have something here,' and they commissioned us to find out what was there."

The survey in Chicago by Bernhardt-Hidvegi's firm, Corporate Art Source Inc., was like a scavenger hunt, she said.

"We went from attic to boiler room in nearly 600 schools," she said. "We would photograph them, measure them, make notations on the condition of everything, including the frame."

In one case, she said, they discovered that a janitor had inadvertently saved a piece as an office treasure of sorts.

"He had seen it near a dumpster and retrieved it, hanging it on a chain-link fence in a boiler room," she said. That painting may well be worth tens of thousands of dollars, she said. "In some cases, it's just that no one knew what these things were worth -- or maybe even didn't care. They would be taken down, for instance, when walls were painted in the summer, and put in a closet. School would start and no one would put them back up, so they would stay in the closet forever."

Reports in Chicago said the art there might be worth about $15 million, but Bernhardt-Hidvegi said the Philadelphia and Chicago school collections differ substantially.

"Our Chicago collection has more murals. Philadelphia has more charming, beautiful and sought-after easel paintings," Bernhardt-Hidvegi said. "Easel paintings have more market value. They can be lent out to museums and, of course, be sold more easily. Murals will tend to stay on walls where they are and some can't be removed at all."

The Philadelphia School District has no intention of selling any of the artwork right now, said spokesman Fernando Gallard. In addition to works by Eakins, there are others by seminal African American artist Henry Ossawa Tanner and N.C. Wyeth, of that painting dynasty. Some of the more valuable works are now in storage in secret locations, he said, and the district is setting up an advisory committee to consider what should be done with the collection.

One member of that committee is Adrienne Neszmelyi-Romano, the associate curator for education at the James A. Michener Art Museum in Doylestown, Pa., about 20 miles north of Philadelphia. For the past 10 years, the Michener museum has supervised the Bucks County school system's collection, which has 300 pieces and was started in the 1950s and 1960s by Charles Boehm, then the county superintendent. Boehm used $500 to $1,000 a year in district funds to buy original art from the colony of expatriate New Yorkers and Philadelphians who settled in relatively rural Bucks County.

"The original mission for the collection from Dr. Boehm, who worked with Walter Baum, a Pennsylvania impressionist, was to have a traveling art gallery to educate schoolchildren about the local Bucks County art heritage," Neszmelyi-Romano said. She now curates programs in the local schools, lending out six or eight varied pieces for about six weeks at a time. Teachers then follow an interdisciplinary curriculum to go with the pieces. "They might write a poem about a piece and then learn the technology of how paintings are preserved, and then draw something inspired by it. I think Philadelphia can use what it has found in similar ways to enhance art education."

Boston and Pittsburgh are taking stock of whatever art might be in their schools. A spokeswoman for the Washington, D.C., schools knew of no special effort being made there. But Gallard of the Philadelphia School District said no one should view the alleged monetary value of the Philadelphia collection as a particular financial bonanza. For one thing, Chicago spent about $3 million to rehabilitate and store its collection. For another, he said, the point is to use the collection, not sell it off.

"This is a time capsule of Philadelphia art. It is a valuable resource, but as history and education," he said. Most of the art was collected or donated from the early 1900s through the 1950s, when alumni and principals did so as a matter of course, Gallard said. "We're hoping to find ways of using these discoveries as a way to inspire current students."

Robyn Sims, president of the Woodrow Wilson Middle School Home and School Association, points out damage done to "Lunch," a Catherine Morris Wright painting that is one of many original works in Philadelphia schools.