Now is the time to learn new subjects and explore new ideas and even “color outside the lines” a bit to prepare for college and beyond, President Barack Obama said Wednesday in his annual back-to-school speech to U.S. students.

It was the third straight year Obama has visited a school to deliver a speech — also broadcast on the Internet across the country — that encouraged students to work hard and set high goals.

“I don’t want to be another adult who stands up and lectures you like you’re just kids, because you’re not just kids,” Obama told a packed auditorium at Benjamin Banneker Academic High School. “You’re this country’s future. You’re young leaders, and whether we fall behind or race ahead as a nation is going to depend, in large part, on you.”

In 2009, his first year as president, Obama’s plan to deliver a similar message prompted an unexpected backlash from conservatives who worried that he would push students to support his political agenda.

However, the speech Obama delivered at a Virginia school that year included no political references and was welcomed by conservatives. There was no similar controversy surrounding his speeches to kick off the school year in 2010 and this year.

Obama encouraged students to make the most of the school opportunity to find out what interests them.

“You’ve got to wonder. You’ve got to question. You’ve got to explore. And every once in while, you’ve got to color outside of the lines,” Obama said, adding: “That’s what school is for: discovering new passions, acquiring the skills, making use of this incredible time that you have to prepare yourself and give yourself the skills that you’re going to need to pursue the kind of careers that you want.”

As in the past two years, he referred to some tough times in his own student life, when he cared more about basketball than his classes. One particular class in ethics, which he cared little for at the time, opened his mind to broader questions of right and wrong that he still considers today in his role as president, he said.

“If I’d just tuned out because the class sounded boring, I might have missed out on something that not only did I turn out enjoying but has ended up serving me in good stead for the rest of my life,” Obama said.

The president also emphasized that education doesn’t stop after high school, telling the students that to be competitive in the modern world requires further study at a university or community college or getting a professional credential or training.

“You have to not only graduate, but you’ve got to keep going after you graduate,” he said. “The fact of the matter is that more than 60 percent of the jobs in the next decade will require more than a high school diploma. More than 60 percent. That’s the world that you’re walking into.”

He added for emphasis: “You are not done learning.”