First lady Michelle Obama told Denver students Monday that there is a sure-fire way to succeed: hard work, focus and confidence.

Speaking at a luncheon for high school girls at the governor’s mansion and at a sit-down with students at South High School, Obama urged the teenagers to reach their potential, seek out mentors and be role models for kids younger than themselves.

“Be at school. Work hard. And don’t let anybody doubt you,” she said. “I want each of you to think about what you’re going to give back.”

“There’s no way that I could have known at your age that I would be standing here as first lady. What I did know was that I wanted to make my family and my community proud,” she said.

The Princeton University graduate, in town for a day of mentoring, also let some of the students at South High School in on a secret: She never performed “great” on standardized tests. Straight A’s, student government, sports, teacher recommendations and her essays are what led her to the Ivy League.

But while Obama said she didn’t consider the tests a good indicator of future success, she told the students that they are “part of the system” and need to be taken seriously.

And she urged them to focus on the thing they have most control over: their grades.

“Fundamentally, the difference between an A and a B oftentimes is in your own hands,” she said, responding to a student’s question about whether it was fair to use test scores as the measure of school performance when many kids can’t speak English.

“So if you use what you have and you make the most of the opportunities that you have control over, then things like test scores don’t have to completely throw you off,” she said.

The first lady’s visit to Denver was part of a mentoring program she launched Nov. 2, when more than a dozen high school girls from the Washington, D.C., area came to the White House and met with Obama and members of her staff.

Cabinet officials, scientists, actresses, politicians and an astronaut met with 80 high school girls at the governor’s mansion for a lunch of butternut-squash soup and baked chicken. The girls were chosen by their respective schools based on who the faculty thought might benefit the most from the experience.

Noting all the successful women in the room, the first lady told the girls that the women’s achievements did not come easily.

“For each of us, we’ve all failed. We’ve all made mistakes,” Obama told the girls. “What we didn’t do was let those mistakes shatter us and keep us from moving on to the next set of challenges.”

Alex Pash, 16, is on the tennis team at East High School and aspires to be a news broadcaster after college. Seeing the first lady, she said, was a chance of a lifetime.

“I just think she is incredible. She has style and passion about what she’s doing,” Pash said.

After the luncheon, Obama visited South High School, and the group of mentors visited 10 other metro-area schools.

Media access at the schools (the majority of which are public) was limited to a handful of initial questions. Reporters were then asked to leave as politicians and celebrities continued to speak with students.

Obama and about 30 students at South gathered their wooden chairs in a circle, and the first lady took questions.

One student asked her what was the most difficult part of being first lady.

“You’re always struggling with making sure that you’re doing right by the country, but you’re also doing right by your kids,” Obama said, noting that she and the president always make sure they are available for their daughters, Malia, 11, and Sasha, 8. “That means when they have an event, it takes precedence over everything.

“I want to make sure they come out of this as whole as possible.”

Karen E. Crummy: 303-954-1594 or kcrummy@denverpost.com