Heather Klein was in her cabin at Camp Nah-Jee-Wah, nursing her first iced tea of the morning, when a photograph arrived on her phone and she drew a deep, sudden breath.

Ms. Klein, the mental-health coordinator for a network of sleep-away camps, has a morning routine: responding to queries from anxious parents, who have looked at the photographs posted online the night before. Why does my child look sad? they want to know. Where are their friends?

This message was from a counselor — and it was serious. A teenage camper had switched from high-tops to Crocs to go to the beach, which allowed her counselor to see a row of cuts the girl had made with a razor.

Ms. Klein pulled up the girl’s medical forms, which noted that she had been in therapy for anxiety and depression but made no mention of self-harm. “OK,” she said. “She’s going to have to go home.”

In her role at NJY Camps, a network of Jewish overnight camps in Pennsylvania, Ms. Klein spends her days sorting serious risks, ordinary unhappiness and squalls of parental anxiety.

All day, as campers move in flocks from the dining hall to swimming, to crafts and archery, to their bunks, Ms. Klein zips around camp in a golf cart, outfitted with a fanny pack and a walkie-talkie.

Summer camp has always involved a degree of emotional struggle. Homesickness is overcome; high dives braved; bunk mates won over. When adults in the industry refer to a “successful camper,” they often mean one who sticks it out.

But youth mental illness is an urgent problem in this country, a challenge the surgeon general has described as “the defining public health crisis of our time.” Between 2001 and 2019, the suicide rate for Americans aged 10 to 19 jumped by 40 percent, and emergency-room visits for self-harm rose by 88 percent.

During the pandemic summers, many camp directors say, campers arrived with mental issues of a severity they had not seen before, exceeding the capacity of counselors in their teens and 20s.

Kelly Rossebo, the director of Camp Eagle Ridge in Mellen, Wis., recalled a single night in 2021 when she and her mental-health specialist “tag-teamed back and forth” for hours, addressing problems that included suicidal ideation, eating disorders and binge drinking.

Since then, she said, “I have certainly had to have harder conversations with parents about whether we’re the right fit for their child.”

“We’re a leadership camp; we’re not a therapeutic camp,” she added. “I wouldn’t necessarily want to change that demographic. I’m not looking to say, ‘Send us your kids who are struggling, because we’re awesome at it.’”

As the pandemic recedes, many camps are adding mental supports. Some have care teams that meet regularly to discuss interpersonal dynamics among bunkmates. Many set aside time and space for therapy via video during the day. And many camps have created new staff positions focused full time on mental health.

At the NJY camps, which are affiliated with New Jersey’s Jewish Community Centers, among other partners, that person is Ms. Klein, 51.

A familiar face at NJY, where she has served in various capacities for 15 years, she now focuses year-round on mental-health issues for the network, a position funded by the Healthcare Foundation of New Jersey. A day spent in her company, from 7 a.m. to midnight, offers a glimpse into an increasingly complex juggling act.

7:23 a.m.: ‘Big love’

“Those are fresh wounds,” Ms. Klein said, peering at the photograph the counselor had sent her, showing a row of reddish cuts on a bare ankle. She felt for the girl and her family, but the camp had a policy: Campers engaging in active self-harm would be sent home.

“We are not a therapeutic environment,” she said. She keeps an eye out for campers who arrive with the stack of bracelets known as “camp wrist,” which can conceal scars, or who wear pants all the time and may be cutting their legs.

The camp’s intake forms now ask a specific question: Has your child demonstrated any unsafe behaviors? But parents, she said, don’t always tell the whole story. They “want their kids to be able to go and do, and don’t realize the importance of us having all the information.”

Over the phone, she talked the counselor through the next steps, starting with the pickup by a family member. “Let’s make sure she is safe and watched and with a staff person at all times,” Ms. Klein said. “I’m sending you big love.”

Just like that, the teenager’s camp summer was over. And Ms. Klein was needed in Bunk 50.

8:12 a.m.: Breakfast meds

Much of Ms. Klein’s day is spent on standard camp fare: In Bunk 15, a camper flushed his bunkmate’s glasses down the toilet. There were dizzying violations of the “no back/no boobs/no butts/no bellies” rule and skirmishes over Jibbitz, the plastic charms that decorate Crocs.

Of the 2,200 children and teens who attend NJY camps in the summer, around 20 percent take medication for attention deficit hyperactivity disorder and 15 percent for anxiety and depression, according to the medical staff. Twenty-five to 30 meet remotely with therapists during camp sessions.

Outside the dining hall, a nurse called out, “Breakfast meds,” and a line of children formed. This, Ms. Klein said, is simply part of the fabric of childhood. Last month, when an 11-year-old camper began misbehaving, Ms. Klein called a bunk meeting and explained to the other children what had happened: The girl had been on a “medication vacation,” and it wasn’t working out.

“I said, ‘Do you know what A.D.H.D. is?’” she said. “They said, ‘Oh, yeah, my mom has that. My therapist told me about that.’ Kids know what is going on.”

In recent years, campers have arrived at camp with a sophisticated clinical vocabulary that they have picked up from their peers and TikTok. “They exchange these high-level concepts with each other,” Ms. Klein said.

This can cause ordinary moments to escalate. “A kid that is just crying and has lost their breath because of crying, the counselor is like, ‘She’s having a panic attack,’” Ms. Klein said. “No.”

This is part of the problem, she added: “They’re all so therapized.”

12:39 p.m.: Struggle muscles

“She was definitely crying before bed,” Ms. Klein said on the phone to a mother. It was a delicate balance; before drop-off the previous day, the girl’s mother had told her she could come home if she wasn’t happy.

Ms. Klein was intent on shoring them up, mother and daughter. “I really don’t think she needs to go home,” she told the mother. “I want her to use those struggle muscles and understand she can do hard things.”

Homesickness has always been part of camp, but in recent years it has become more acute and difficult to manage, she said, perhaps because of the habit of constant communication between parents and kids.

“We used to work with parents and say, ‘We can get your child through this,’” she said. “Parents used to trust us much more.”

In 2021, well into the pandemic, between 35 and 40 children were sent home from NJY camps because of homesickness or anxiety, which was a record for the camp and part of the reason Ms. Klein’s job was created.

Ms. Klein was trying to keep the girl at camp. They conferred on her golf cart and on the sidelines at a barbecue. There was a flurry of telephone calls between adults: The camp director and the girl’s mother. The camp director and Ms. Klein.

“When you said you can reassess in a few days, that is really giving her the option to not be here,” Ms. Klein told the mother. “If I don’t have your backing on that, I may as well pack her up right now.” Later, the girl’s mother sent a text asking Ms. Klein to keep her distance.

She would pick up her daughter the next day.

4 p.m.: Blood oxygen

In the infirmary, a curly-haired boy had reported nausea, vomiting and difficulty breathing, and also that when he closed his eyes, he saw the color cyan. He thought it would be a good idea to check his blood oxygen levels.

Ms. Klein knew the boy. “Mom says he fabricates,” she said. She checked his temperature and led him back to the golf cart. “I think what you’re feeling is nervousness,” she told him, and then dropped him at the nature center.

A call came in from Round Lake Camp, which is for children with learning differences, social communication disorders and A.D.H.D. A camper was curled on a porch, gasping for air and crying out, “I’m vibrating!”

Ms. Klein stroked the camper’s leg. “Breathe in like you’re smelling a pizza,” she said. “I want to see your belly moving up and down.”

A report of a suspected eating disorder was, she determined, a false alarm. After dispatching that case, she found an 8-year-old in pigtails sitting cross-legged on the pavement. “I don’t like the feeling of camp,” she said. “It feels weird.”

In past years, counselors might have handled these situations, but the counselors themselves are stressed out, she said. “They have lost the ability to use their struggle muscles,” she said. “They just want someone to come in and fix it.”

Later, the pigtailed girl refused to leave her bunk, and Ms. Klein took her to the infirmary for a temperature check. “There’s going to be a little placebo effect here,” she said cheerfully, and returned the girl to her bunkmates at the amphitheater.

9 p.m.: Emotional support rabbit

Ms. Klein did not love camp as a child. She remembers sitting, alone and miserable, on the porch of her bunk; if the staff sought her out to comfort her, she has forgotten it.

She persuaded her parents to bring her home early, but she felt, for years after that, that she had fallen short.

This is what she wants to prevent, she said. “I often tell parents whose kids are struggling, if they quit, they will feel like failures, and we don’t want them to feel that way,” she said.

She tries to convey to the children that sadness is transient, that it can exist alongside happiness, “that it’s OK to have two feelings at the same time.” When she was a camper, she said, “nobody gave me those words.”

At 9 p.m., insects wheeled in the flood lights above the tennis courts. Senior staff had flopped down on the couch in Ms. Klein’s office, discussing a camper who had been sent home for flashing a gang sign. They were all exhausted.

Then word came in that two vapes had been found in a camper’s backpack, one nicotine and another marijuana, a violation of camp rules serious enough to require the attention of the chief executive.

“I got to call Michael on this,” Ms. Klein said, but it killed her: This teenager had been at camp two years ago when word came in that her mother had died. Ms. Klein had helped pack her up to go home then, too.

The camper headed to the infirmary, dangling a stuffed animal. “Emotional support rabbit,” said a label on its chest.

Ms. Klein watched her leave and covered her face with her hands. Then she rested her elbows on the top of a bookshelf and wept.