Mercersburg Academy announced the contribution from alumna Deborah Joy Simon, who graduated from the private boarding school in 1974. She now serves on its board of regents.
"To me, the school was a lifesaver," Simon said. "It was like a home away from home."
The funds will be used to boost financial aid, support faculty development, and enhance facilities and programs, said Douglas Hale, the top administrator at Mercersburg. He expressed profound appreciation for the gift, which comes during an ambitious $300 million fundraising campaign.
"It affirms that what we're doing is important work and worthwhile work, and it really transforms young people's lives," Hale said.
One goal is to make the school need-blind, meaning applicants' ability to pay would not be considered in the admissions process, he said. Nearly half the student body receives some type of financial aid to attend Mercersburg, which costs almost $51,000 a year.
Simon said she arrived at the school during a difficult time in her young life and found it to be "one of the most magical places I've ever been." She later joined her family's real estate firm, Indianapolis-based Simon Property Group, and then worked in the entertainment industry for years. She currently runs the Simon Youth Foundation, an organization for at-risk teens.
Her donation comes in three parts: a $50 million contribution, $25 million in matching funds, and a $25 million estate commitment.
The gift comes six years after the private George School in Newtown, a Philadelphia suburb, received $128.5 million, believed to be the largest gift ever to a U.S. secondary school. It came from alumna Barbara Dodd Anderson, whose father had been a business partner of billionaire investor Warren Buffett.
In 1993, publisher Walter Annenberg gave $100 million to the Peddie School, a prep academy he attended in Hightstown, N.J.
Hale said that while places like universities and museums are frequently targeted for philanthropy, Simon's donation should remind would-be benefactors of smaller but equally worthy recipients. All told, Simon has given more than $111 million to Mercersburg.
"I hope it will help people to step back and realize those places in their lives that have been formative for them," Hale said. "Those places need support."
Mercersburg Academy serves nearly 450 students in grades nine through 12. Notable alumni include Oscar winners Jimmy Stewart and Benicio del Toro, as well as cable TV mogul H.F. "Gerry" Lenfest, who gave the school $35 million in 2000.
Its campus sits about 150 miles west of Philadelphia, near the Maryland state line.