Hixson High School junior Allison Mitchell isn't concerned with earning a perfect grade-point average.

She's headed to college and plans to study optometry but is pretty sure a 4.0 won't make her stand out.

Instead, she's focusing her efforts on taking the hardest classes she can find, including Hixson's Advanced Placement U.S. History.

"I get bored in the regular history class," she said. "Everyone is trying to get into college. You've got to have something to set you apart."

Throughout her high school career, Ms. Mitchell, 16, has known what a recent study by the Center for Public Education recently confirmed: when it comes to getting into college, it's more important for students to take a challenging course load than to earn a perfect GPA.

Lots of students get good grades, says Ms. Mitchell's history teacher, Suzanne Rushworth. And the competitive world of college admissions, sometimes that's not enough.

"When (college admissions officers) see Advanced Placement on (a transcript), that tells them something about a student's motivation," she said. "And working hard may not get that student an "A." It's a college-level course, but AP goes beyond that."

On a Thursday in AP U.S. History, students spent class time reading newspaper articles, then writing and presenting essays comparing the current events to historical events or issues about which they've read.

The following day they had a test over Elie Wiesel's Holocaust memoir "Night."

"I wrote the curriculum and had to get it approved by the College Board," Ms. Rushworth said.

The College Board, a nonprofit organization that offers programs such as the SAT and AP classes, actually recommends that teachers add five extra points to an AP student's final grade, so students aren't penalized for taking the harder class.

"It works out well because a student usually ends up getting what they would have gotten in the non-AP class," Ms. Rushworth said.

For all the emphasis she puts on a rigorous curriculum, Ms. Rushworth is the first to admit that a strong GPA is also important because that determines whether a student is eligible to receive Tennessee's HOPE scholarship.

Lee Pierce, the associate director in UTC's undergraduate admissions office, said "in theory" the University of Tennessee at Chattanooga places a higher priority on harder classes by honoring the weighted GPAs high schools often award for AP courses.

"We are giving them credit for doing the extra," she said.

Ms. Rushworth said she encourages students, telling them that AP courses will make students better learners and more prepared for college.

"I tell them that now is the time to stretch yourself while you have so many people around who can help you. The safety net gets a little smaller in college."

Ms. Mitchell said she's also had a similar pep talk from her older brother, who is in college.

"He says there's more studying in college," she said. "(Ms. Rushworth) doesn't baby us. My brother says that's what college is like."

Fellow Hixson junior Vanessa Parras, 17, said part of the appeal of the harder classes is the college credit students can earn if they pass the AP exam in a subject.

"Get college credit, get out of college faster," she said. "It's good experience."

Follow Kelli Gauthier on Twitter at twitter.com/gauthierkelli