Some had tears in their eyes. Some had chills. Some tried to be dignified but couldn't stop themselves from whooping and hollering for the leader of the free world, standing just a few feet away and telling them he was proud of them.

To Antoine Smith, graduating from Science Leadership Academy on Monday night and then being in the same room with President Obama on Tuesday night was "surreal."

"I was thinking, 'Yo, that's the man who runs things. This is the dude who runs everything,' " said Smith, 18, who is headed to Delaware State University in the fall.

"I didn't want to breathe," said Alexis Beckton. "The whole time."

Before he hobnobbed with campaign donors at the Franklin Institute, the president spoke to the newly minted graduates of SLA, a city public school that operates in partnership with the science museum.

Obama said that the students' talents would mean a bright future for the United States.

"My expectation is that somebody in this auditorium is going to figure out new sources of energy that help not only make us more energy independent but also deals with the problems like climate change," the president said. "There is somebody in this room who is going to make sure that we are defeating diseases like Alzheimer's or find a cure for cancer."

Established just six years ago, SLA - a project-based high school that focuses on science, technology, math, and entrepreneurship - has attracted national attention for its innovative practices.

Big names don't faze the 122 seniors, who met Bill Gates when they were sophomores. They're used to high-level discussions, work that matters, visitors trooping in and out of their classrooms.

But this was special.

And, no, Alaya White vowed, she is not washing her hand.

White was one of a handful of students who got to shake hands with the president. When she saw Obama, she couldn't hold back - she screamed and clapped as loudly as she could.

"Every time he mentioned something about science and innovators and the future, I smiled," said White, 17, who will study biochemistry at Drexel University.

SLA is an elite school by virtue of its admission standards, but it is also a real-world place. A few of the seniors could not attend because they had to work.

And Obama gave a nod to the school's diversity - 46 percent of its students are African American, 33 percent are white, 10 percent are Asian, 10 percent are Latino.

That is an "incredible strength for the United States, because innovation, brain power, does not discriminate by gender or race or faith or background. Everybody's got the capacity to create and improve our lives in so many ways. . . . This is a great postcard for what American is all about," Obama said.

Alexis Beckton, 17 and planning to study psychology at Johnson C. Smith University in Charlotte, N.C., said that, in some ways, the president felt like "part of the family."

He mentioned his daughters by name, talking about how Malia and Sasha know more about the Internet than he does and how "the fact that you've come of age in this new information age gives you an enormous advantage over old fogies like us."

"I've always seen Obama as a father figure," Beckton said. "He made me tear up a bit. I felt so important."

Engineering teacher Matt VanKouwenberg appreciated the president's tone. He also loved watching the students' faces when the speech was over.

"They were just radiating joy," VanKouwenberg said.

After the brief speech - less than 10 minutes elapsed from when Obama entered Franklin Hall to the moment he left - the teenagers walked back in a drizzling rain to their school at 22d and Arch. Many lingered in the office of principal Chris Lehmann, who was honored by the White House as a "Champion of Change" last fall.

Obama's "important charge" will resonate with these young people for years to come, Lehmann predicted.

"They will look at this," he said, "as a signpost moment in their lives."

Inquirer staff writer Thomas Fitzgerald contributed to this article.