"We want to have $1 million in hand" when the school outlines a plan to show that it can be viable for years, Olson said.
The school wants eventually to raise at least $5 million to guarantee its future, he said. "We have 38,000 alumni," Olson said. "I believe we can do it."
On Jan. 6, a Blue Ribbon Commission set up by the Archdiocese listed Bonner-Prendergast as one of four high schools and 45 elementary schools recommended for closing because of declining enrollments in the five-county region.
Although the school has operated in recent years as one high school with one administration, the traditionally all-girls Prendergast is in one building and the all-boys Bonner in another. The 33-acre campus sits on a hilltop off Lansdowne Avenue at Garrett Road.
Olson said the school plans to bring boys and girls together in the Bonner building.
"We have also issued an invitation to the students of West Catholic to join us," Olson said.
Students had sent text messages and Facebook announcements to return to school at 4:30 p.m. for Thursday's announcement. They cheered and applauded when Olson said the school would appeal.
He also said he met and prayed with Archbishop Charles Chaput over how to handle the community's pain at being on the closure list.
"I now feel really at peace" about the decision, he said.
Karen Friel, a 1975 Prendergast graduate and the mother of a freshman son at Bonner, said the people support the school's plan.
"I just think the same-sex education that Prendergrast and Bonner give children provides them with what they need to become successful in life," said Friel, a Drexel Hill lawyer. "I know it has for me."
Olson said the school may consider retaining separate all-male and all-female classes in the one building.
Matt Gelbach, 16, a junior, said students are happy about the appeal. "I was overjoyed when I heard about it," Gelbach said. "We can do this.
"This is my third year here, and I don't want it to close. It will be hard to be a senior [next year] at a new school."
Mike Shanahan, 15, a sophomore, said the school is worth fighting for: "It's a good school. My whole family, my aunts and uncles went here."