At 5280 High School in Denver, the morning bell gives way to a different kind of assembly for the first day of school. The students, most of whom have histories with substance abuse, huddle on the steps of the auditorium. They are gathered for a school-wide recovery meeting.

       "When we're talking about sobriety, we're talking about all mind-altering substances, including [weed]" Keith Hayes, director of recovery for the Colorado school, told them.

       With the uptick in deadly narcotics like fentanyl being mixed into street drugs, he had a dire warning for the teens.

       "Here's the thing for all my coke heads out there… that line could be your last, permanently," he said.

       According to the National Center for Drug Abuse Statistics, 2.9 million kids in the U.S. between 12 and 17 need substance abuse treatment. Yet, there are only 43 recovery high schools nationwide, along with around 160 residential treatment programs.

       With 109 students enrolled in the 2024-2025 school year, 5280 High School is one of the nation's largest. The charter school, funded by Denver Public Schools and private donations, opened its doors in 2018. The school says students must be committed to their sobriety in order to attend. Once they are stable, the academics come into focus. According to 5280, 70% of the student body has been sober for at least 6 months.

       "I have a team of recovery coaches... they're all individuals today who are in long and sustained recovery. And they do individual case management with our young people. It's [like] having a sponsor here at school on a day-to-day basis" Hayes told "Nightline."

       He noted that he, too, is eight years sober after 20 years of active addiction to alcohol and cocaine.

       "Our goal is to help kids get sober, stay sober, find purpose and passion in their recovery, all while getting their high school diploma," he said.

       Twins Ben and Clara Leoni are graduating seniors at 5280.

       "It's amazing how much they're doing for the community and people in recovery. But also it's a school where it helps me kind of learn the way that I need to learn" Ben, who is dyslexic, told "Nightline."

       Clara expressed her appreciation for the school's support system.

       "If I'm struggling, I know I can go to my teachers or I can go to [my] classmates. So… you always feel like you can lean on somebody" she said.

       Nightline followed several students closely through the school year. Conor Schroeder, 18, is a senior in his fifth year of high school who is striving to graduate. Conor, who is in recovery from marijuana, alcohol and benzodiazepines, told "Nightline" that, before attending 5280, he used to go to school just to score drugs.

       "I got suspended for fighting multiple times… I had moved into sophomore year with a 0.014 GPA," he said.

       Conor told "Nightline" that he grew up surrounded by a world of drugs. His mother, who is now in recovery, used to abuse Xanax, cocaine and alcohol. According to Conor, his father grew weed in their suburban Denver home before it was legalized in Colorado.

       "The first time I ever got high I was 8," he said.

       According to Conor, his drug use started to escalate when he was 12.

       "My friends used to call me 'Popper' because I literally would, like, take unnamed pills… like I wouldn't know what they were," he said.

       After run-ins with the law for breaking into cars and countless drug-fueled benders, Conor reached out to his mom, who had been sober for years by that time, for help in 2022.

       "I was like 'I don't think I could do this anymore'… and so she told me about 5280," he said

       The school, which helps students recover credits to get back on track with their education, was able to offer him the opportunity to graduate this year. In October 2024, he celebrated two years of sobriety. His mother, Ceara McAllister, marked her 5th year in recovery days later.

       "It's super special being able to celebrate these milestones with him" she told "Nightline."

       Conor, who attends a separate recovery group "Full Circle" outside school, said he hopes to work there one day and applied for an internship.

       "[Full Circle has] given me a purpose that I don't think I could ever find somewhere else" he said.

       Lele Mayfield, 17, is also a senior at 5280 High School. Lele lived with different family members after her mother died when she was just 2 years old. When she lost her aunt in 2023, she said her weed and alcohol use spiraled into addiction.

       "I got into a very, very depressive state after my auntie passed away…if I would've continued to do what I did [at] another school and didn't go to 5280, I don't think I would have been sober," she told "Nightline."

       Lele's cousin became her legal guardian, took her into her home and enrolled her in 5280 in October 2023. She was able to recover several missing credits to graduate on time and marked one year of sobriety in January.

       Although she has found support through 5280's afterschool recovery program "Altitude," Lele admitted she still faces occasional struggles.

       "I've had to find so many different new ways to like cope with my emotions, situations and stuff like that without having to use weed or alcohol and that's been hard," she said.

       Originally from Texas, 17-year-old Morgan Hedrick is a junior at 5280 High School. She told "Nightline" that she was introduced to crystal meth at a sleepover when she was 13 years old and quickly lost control of her life.

       "I was a meth addict who had hardly any ways of getting what I needed. So I got myself into like a lot of trouble… I was selling nudes, you know. They got leaked" she told "Nightline." "I was actively getting blackmailed with my nudes while I was in school."

       Morgan's parents exhausted their finances to get her the help she needed, she noted. When they ran out of affordable options in Texas, they set their sights on Colorado.

       "We moved here for 5280. [Morgan's stepdad] talked to Keith and Keith was like: 'Just bring her, just get her here. We got her.' [We were] relieved and hopeful. I mean, it was scary. It was scary moving here" Morgan's mother, Christina Hedrick, told "Nightline."

       The family moved to Centennial State in 2022.

       "I'm like eternally grateful to them for that" Morgan said.

       She celebrated two years of sobriety in December 2024. Morgan also attends Full Circle meetings with Conor and said she hopes to work at 5280 when she finishes school at the end of the year.

       "I absolutely want to work in recovery… that's the sole thing I found my purpose in," she said.

       Anthony Montano, an 18-year-old sophomore, entered the school year with a lot at stake. In recovery from a fentanyl, crystal meth and alcohol addiction, he's on probation and faces potential jail time.

       In addition to possible incarceration, his girlfriend at the time had just given birth to his first child -- a son. Anthony's struggles began after he wound up homeless on the streets of Denver at just 13-years-old. He showed "Nightline" the bus stop he said he slept at.

       "I would have nowhere to go just walking up and down these streets," he said. "I had a bag full of clothes… I sat here for about maybe four or five days."

       Anthony's father was in prison and his mother struggled with an alcohol addiction' both were unable to take care of him. While living on the streets, he said he met someone who recruited him into a gang.

       "He taught me how to, you know, sell dope and stuff, and what to do, and how he made money," he said.

       Anthony also was introduced to meth. The lifestyle took its toll on Anthony, who bounced between motels, arrests and stints in juvenile detention. When his mother passed away in 2022, he immediately turned to fentanyl.

       "I was broken, I lost part of me," he said. "And then [I] started sniffing the fentanyl [and] overdosed right away… eventually I woke up [to] people all around me, CPR and narcans."

       Anthony resorted to stealing and ended up back behind bars for the final time, at 17, in December 2023. This time, his older half brother, Tomas Salazar, took him in after Anthony's release in March 2024.

       "It was really a wake-up call for me. I'm like… I need to be the big brother that he needs," Salazar told "Nightline."

       Anthony enrolled in 5280 as a requirement of his probation. Seven months into the school year, Anthony faced a crisis when his infant son was allegedly exposed to fentanyl at the home of the child's mother in March 2025, according to police reports. She pleaded guilty to one count of child abuse resulting in serious bodily injury and is awaiting sentencing. She declined to speak to ABC News.

       Anthony's son was revived with Narcan and hospitalized. He was granted custody.

       "He's very lucky… if he didn't come back, I think I would have lost it" Anthony said.

       Despite many setbacks during the school year, including a brief relapse on meth last September, Anthony completed the school year and celebrated five months of sobriety in April 2025. His probation ends in November 2025 and he hopes to enlist in the Army after he gets his diploma.

       "I look at myself in the mirror and I see who I am today [and] I'm like, I changed, I know I'm a better person now," he said.

       ABC News' Jeff Cook and Mola Lenghi also contributed to this report.