PHILADELPHIA — For his second annual back-to-school speech, President Obama chose as his backdrop an elite, selective public school in this city that is a far cry from the turnaround-success stories his administration is seeking to promote.

Obama, in a Tuesday afternoon speech, urged the nation’s students to “dream big” and “stay focused” on education in an address that aides described as a nonpolitical event.

But students at Philadelphia’s Julia R. Masterman Laboratory and Demonstration School probably are already heeding that advice. The school, with about 1,200 students from grades five through 12, draws the city’s academic cream through competitive admissions.

Tuesday’s speech steered clear of politics, yet it touched on some themes on the minds of voters in the run-up to the midterm elections.

“I know a lot of you are also feeling the strain of these difficult times,” Obama said in the prepared text. “You know what’s going on in the news and your own family’s lives. You read about the war in Afghanistan. You hear about the recession we’ve been through. You see it in your parents’ faces and sense it in their voice.”

But the president exhorted the students: “Your future is in your hands. Your life is what you make of it. And nothing — absolutely nothing — is beyond your reach. So long as you’re willing to dream big. So long as you’re willing to work hard. So long as you’re willing to stay focused on your education.”

Last year, Obama gave a similar televised pep talk at Wakefield High School in Arlington.