Kelly Wallace is CNN's digital correspondent and editor-at-large covering family, career and life. Read her other columns and follow her reports at CNN Parents and on Twitter.

(CNN) At the start of the school year at Marblehead High School in Massachusetts, students started moving their desks out of the way, grabbing a mat and laying down on the floor for guided meditation before French class. Lexxi Seay, a senior, was skeptical.

"I actually never believed really in meditation. ... I thought it was a joke," she said during an interview.

That all changed one day back in September. While she was on her computer working and everyone else in her class was meditating, she just fell asleep sitting up. "When I woke up, I was like, 'What happened?' ... It just completely relaxed me."

Ever since then, every day before French class, she grabs a mat, lies on the floor and listens to her teacher, Violaine Gueritault, telling her and her classmates to clear their minds as she guides them through a process of relaxing each part of their body.

"It helps so much. It really does," said Lexxi, 18, who has been diagnosed with anxiety disorders. "I tend to be less anxious afterwards. Let's say I am having a real hard day at school and then I go to French and we meditate for 10 to 15 minutes, I feel so much better. No anxiety, no stress, just relaxed."

The guided meditations are all part of a fast growing trend in education, where more schools are providing mindfulness exercises to students and teachers in response to the enormous pressures students are facing.

The drive to get good grades and gain acceptance into elite colleges, combined with participation on sports teams and other after-school activities, and hours of homework mix together to make teenagers the most stressed group of people in America when school is in session, according to a 2014 American Psychological Association survey

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"A lot of it started when I started off as principal here. We had these forum meetings with the parents, and one of the patterns that came up over and over again was this idea of the great stress that the students were under," said Layne Millington, principal of Marblehead High School.

Gueritault, who is a psychologist and a passionate advocate of mindfulness, started offering morning meditation sessions two times a week before classes. "I thought a lot of students would make fun of the whole thing, and boy was that a surprise," she said. Instead, the kids were very receptive and very eager. "It was incredible how quickly it snowballed," said the mom of two, ages 18 and 21. (Her daughter graduated from Marblehead High School last year.)

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Gueritault said teachers spoke up and asked "What about us?" And so she started doing workshops for the teachers last spring -- workshops that are now being offered to teachers throughout the district.

Gueritault also taught mindfulness and meditation discovery to students in freshmen and junior year in three hourlong sessions as part of the school's wellness program. And just last week, the school opened what it calls a Zen Room, which will be offered daily from 9 a.m. to 2:30 p.m., complete with yoga mats, blankets, tranquil music and soft lighting, staffed by teachers trained in mindfulness to guide the students during their study hall breaks.

The cost for all the programs, about $16,000, has been covered through grants from the Friends of Marblehead Public Schools and the Marblehead High School Parents' Council.

Students "are just craving for ways to handle and cope with their stress" in healthy and nondestructive ways, said Gueritault. "It becomes sort of like instinctive and intuitive for them to just search for alternative ways to cope with their stress that have nothing to do with drugs or alcohol or whatever destructive behavior."

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Millington, who is in his third year as principal at the school, said the climate at the school is much better after implementing mindfulness. Students who participate seem much more relaxed and easier to talk to, and they can be more precise and more specific if there's something going on that they are concerned about, he said. For many kids today, they don't realize the stress they're under until something comes along and shows them, he added.

"I think that's the reason that the students are latching on to this because when they've had a chance to stop, think, breathe and really kind of feel where they're at, they know how much stress they're under finally and now that they are aware of it, they can try to do something about it," said Millington.

'It's really exploded'

Dr. Dzung Vo is author of "The Mindful Teen."

"When I first started giving talks to schools or to doctors or to parents about mindfulness for teens, most people in the audience had never heard the word and now when I give talks, almost everyone has been hearing about it and quite a few people have actually experienced it for themselves, so it's just been phenomenal," said Vo, a pediatrician specializing in adolescent medicine at British Columbia's Children's Hospital and a clinical assistant professor at the University of British Columbia Faculty of Medicine.

"A large part of being a human being is having social, emotional and attention skills and in the majority of schools I visit, we don't actually teach kids how to pay attention or how to deal with their inner states in a healthy way. We just assume that they'll learn them somewhere else," said Cook-Deegan, who is also an education innovation fellow at the K12 Lab at Stanford's Institute of Design, which is known as the d.school.

While the research on the impact of mindfulness on teenagers is still relatively new and not as comprehensive as the research that has been done on adults, the results from preliminary studies are promising, said Vo.

Mindfulness has been shown to help students have better relationships and more positive behaviors and help them perform better at school, he said. A recent study found it can help students improve their memory. Mindfulness has also been shown to improve teens' physical health and their mental health, said Vo.

Gina Biegel is founder and director of Stressed Teens.

Gina Biegel is a psychotherapist and founder and director of Stressed Teens , which teaches mindfulness skills and provides tools for children in their preteen years and throughout adolescence. She conducted research on the effect of mindfulness-based stress reduction on adolescents 14 to 18 who were under psychiatric care or who had been so in the past.

What she and her fellow researchers found was a reduction in self-reported anxiety, depression, obsessive symptoms and interpersonal problems when teens were given mindfulness training.

Helping students let thoughts 'come and go'

"Mindfulness is another way of looking at life skills. It's really being present to what we're doing," said Biegel, who created an app for teens called Take a Chill and a "Be Mindful" card deck for teens , with 50 ways to be present in your life as it is taking place. What mindfulness does is it helps teens build "from the forces they already have within" and this can boost self-confidence and self-esteem, and lead them to be less focused on judgment, she said.

"If you look at how teens perceive things, perceive and appraise them as stressful, that shifts and changes" with mindfulness, she said.

For instance, something that might feel so stressful and important at that moment, such as "Oh my boyfriend and I broke up and we were going out for four weeks and that is the end of the world," may feel less important and stressful as they learn impermanence and how things change when they sit with them, and how they don't always have to react and respond, she said.

Over a semester of mindfulness training or during a retreat with teens, Cook-Deegan, the educator and speaker who is helping design a new purpose-based high school, said teens begin to notice their thoughts.

And then, you see them come to the realization of "'Oh, you can actually let thoughts come and go, you don't have to cling and hold on to them'," he said. "It's really powerful to watch students realize sometimes for the first time that they don't have to believe every thought that comes into their head."

When people started teaching mindfulness to teens, there was a lot of skepticism, said Vo, the pediatrician and author who teaches an eight-week mindfulness program for teenagers with depression, anxiety and other chronic illness, including chronic pain.

"People thought, 'Oh teenagers are too immature or they're not capable of learning something like mindfulness,' but my experience has been the complete opposite," said Vo.

He tells the story of a teenager who was around 16 and who was missing quite a bit of school and sports because of stomachaches. Through mindfulness, she learned that her stomachaches had a lot to do with her own stress and that she could actually practice mindfulness including short breathing exercises to help cope with her stress and anxiety. One day, when she started to feel sick and her stomach started to hurt, she practiced breathing for three minutes and she started to feel better.

For the rest of the course, she didn't miss a single day of school, which was a "real life-changing experience" for her, said Vo, who is also a board member of the Mindfulness in Education Network, which will be convening a conference in March for educators who are interested in bringing mindfulness to schools.

Today's teens, growing up in a social media world, also don't often realize how much stress all the technology and nonstop noise can cause, said Biegel, who will be taking her mindfulness curriculum to a different state each month beginning in April.

She tells the story of how after one session with teens, one girl had tears in her eyes. When she asked her if she was OK, the teen said, " 'I couldn't stand it. It was so silent in here.' And that was so powerful for me because I realized teens are really never in silence," said Biegel, who also works as a counselor with the Center for Developing Minds in Los Gatos, California.

"They never have this moment just to be with their thoughts, be with who they are and actually what that feels like, to learn how to be comfortable by yourself."

Helping schools be proactive, not reactive

At Woodrow Wilson High School in Portland, Oregon, a course on mindfulness, in conjunction with the nonprofit Peace in Schools, started being offered as an elective last year, said principal Brian Chatard. The school has experienced two suicides by students in the past four years, he said.

"It's just the reality of dealing with the mental and emotional health of teenagers is sort of a missing piece of high school curriculum, and, really, I think, is ... a mission of mine as a high school principal," said Chatard. "My job is to do more than to provide a strong academic program. The lives of these kids are in my hands and so finding outlets for them to know themselves better, to feel good about themselves, to learn strategies for dealing with stress and anxiety is superimportant to kids navigating high school well."

What mindfulness practices do, said Chatard, especially at a school such as Wilson that is very high-achieving, is it allows educators and counselors to give kids the tools to deal with issues such as body image, mental illness and the academic drive for success before those issues take on a dangerous dimension.

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"What it has enabled us is a proactive approach to dealing with the issues that we only end up dealing with reactively, where kids are in crisis and we learn about it because they've attempted suicide or they've stopped coming to school for two weeks or a month or they're cutting themselves," said Chatard, who said he is committed to continuing to offer the program.

Malachi Rosen, another senior at Marblehead High School, started doing the mindfulness and meditation exercises this year, and has done them for about 10 minutes every day before the start of French class since the start of the year.

"Over time, despite being skeptical at first, I started to realize and notice the benefits," he said via email. "I have been a lot less stressed, my level of anxiety has gone down and my ability to focus becomes easier," which he said is "saying something" since he has a ton on his plate with school work, rehearsals for two a capella groups and a drama production, and working at a local coffee shop and at his temple.

"So to become less anxious and stressed on a daily basis is pretty awesome," wrote Rosen, who is 17.

Gueritault says her goal at Marblehead High School and now throughout the district is not to make the teens "expert meditators" but to expose them enough to mindfulness so that on their own, they can go and explore it further.

"What I'm interested in is for this experience to be a springboard for them, some sort of catalyst, just to open a door, to just make them aware that this exists and just to kind of like pique their curiosity," she said. "It's a lifelong skill."

Seay, the student who is suffering from anxiety disorders, said that when she starts college in the fall, she will either learn how to do mindfulness herself or find a class near her school.

"This has helped me so much in these five months that if I don't do it in college, I might explode," she said. "It's so nice."