(CNN) -- Students gather in the gym at Druid Hills Middle School in Atlanta, lay out their mats and get ready to wind down. With deep breaths they lengthen their spines and start to bend -- into cobra pose, downward-facing dog, and eventually into the lotus position.
Emily Schroeder, 11, says doing yoga during the school day helps her feel refreshed and relaxed. More importantly, she says, the breathing helps her build stamina for the other sports she plays.
"I like the way it helps me learn how to control my emotions and just to have fun in life," says Schroeder.
Many school districts are adding yoga to their physical education curriculum to ensure students are meeting the mandated physical fitness requirements. Yoga doesn't require much, if any, equipment, and kids who are less athletically inclined can benefit without the pressure of playing a team sport.
But some parents are fighting the introduction of yoga in schools, saying the practice's religious ties aren't appropriate for government-funded education.
Earlier this summer the National Center for Law and Policy filed a lawsuit on behalf of Stephen and Jennifer Sedlock, whose children attend school in the Encinatas Union School District near San Diego.
Jennifer Sedlock told CNN that 250 community members signed a petition against the practice of Ashtanga yoga in the district's schools. They were worried, Sedlock said, that the yoga classes were religiously affiliated and that students whose parents didn't want them to participate would miss out on physical education altogether if they opted out.
"The concern isn't whether people like yoga or not, the concern is about religious freedom," Sedlock said.
While yoga itself is not a religion, according to the American Yoga Association, its practice has been incorporated into several different belief systems, most primarily Hinduism. Ashtanga means "eight limbs;" the practice was described by a sage named Patanjali in his book "Yoga Sutras" more than 1,500 years ago. Most modern forms of Ashtanga yoga focus on the third limb -- posture, according to Yoga Journal expert Richard Freeman.
Mary Eady, who has a child in first grade in the Encinatas Union School District, said she observed one of the district's yoga classes. While the names of the poses had been changed, she found the "religious ritual" inappropriate for school. She pulled her son out of the program, telling him that it didn't align with the family's chosen religion of Christianity.
"After I did that, he understood and didn't want to participate either," Eady said.
"We don't deny that people use yoga in a religious practice," superintendent Timothy Baird told CNN. "But (the) majority of Americans don't use it for that."
In July, San Diego Superior Court Judge John Meyer ruled in favor of the school district and the yoga programs. In his ruling, Meyer said that the school district had come up with a curriculum for its yoga classes that didn't emphasize religion.
"This is not the end of the road for this case or the last word regarding the fate of yoga in public education," National Center for Law and Policy president Dean Broyles said in a statement at the time. He told CNN the center plans on appealing the ruling.
Sarah Herrington, author of "Om Schooled" and a yoga instructor for children and teens, says there are ways to teach yoga that don't involve spirituality.
"If you really strip it down to the bare bones, it just relates to your body," she says.
Childhood obesity rates have doubled in children and tripled in adolescents in the past 30 years, according to the Centers for Disease Control and Prevention. Programs like First Lady Michelle Obama's Let's Move encourage regular physical fitness activity for kids in hopes of building healthy bones and muscles, controlling their weight, reducing anxiety and increasing self-esteem.
Although it may seem low key, yoga can even provide cardiovascular benefits, says Herrington. The "Sun Salutations" position, for example, cultivates balance and strengthens muscles while working the entire body.
"Little ones as small as age 4 are able to strengthen their motor skills, increase their flexibility and become aware of the difference between their right and left hand," she says. "Anyone can participate in yoga and the exercises can be tweaked so you get a little cardio in there."
With yoga, children learn to self-regulate -- they learn to check in with their bodies, identify their feelings and then learn to give themselves what they need in healthy ways, Herrington says. Many kids snack out of boredom, sadness or tiredness, she notes; when they learn to self-regulate they can make more conscious choices regarding what foods they eat and when.
Children, much like adults, get stressed and need a way to release the tension, says psychiatrist Glenn Kashurba.
"Everyone knows when you exercise you feel better emotionally," says Kashurba. "Biochemically, you release a lot of hormones when you exercise that actually allow you to feel better."
Researchers from Harvard Medical School asked one group of high school students how they felt after a semester-long yoga class. Many of the students who were interviewed enjoyed it and reported being less stressed and having greater control over their negative emotions. Some students also reported having greater respect for their bodies and improved self-image.
Another qualitative study published in The Journal of Behavioral Health Services & Research suggests students who take yoga experience positive changes in their moods and attitudes. The students in this study also reported improvement in their posture, were more relaxed after classes and saw an increase in energy.
"We want them to develop a habit of physical activity and to actually enjoy it," Kashurba says. "It's more important that kids learn, 'Hey, this can be fun.'"