Wende Curtis is used to getting out-of-the-blue texts from superstar comic Dave Chappelle, given that she owns Denver’s nationally renowned Comedy Works clubs.

But she was not prepared for Chappelle’s request last spring that Comedy Works adopt a new cellphone-bagging service as a term of performing at her Larimer Square location, which seats only about 300 people.

“My first thought was ‘That’s weird. People are going to be mad,’ ” Curtis said. “But at the late show that Monday night, I immediately noticed a difference in the crowd. And we’re talking about crowds that are historically a little rowdier and a little more drunk.”

Curtis was not the only one who was impressed with the calming, focusing effects of Yondr, the San Francisco-based service. Other comics, musical acts and even educators have begun experimenting with cellphone-free zones since Yondr debuted in 2014 — from Denver’s Lumineers to comedians such as Chris Rock, who employed the service at his sold-out, 5,000-seat Bellco Theatre show in March.

And as thousands of Denver Public School students return to the classroom this week, some will discover a new obstacle to texting their friends or obsessively updating their social media status during class.

“Like many schools, we’ve had a huge challenge in fighting the cellphone battle,” said Garrett Rosa, principal of Vista Peak Preparatory in Aurora. “People are not experiencing things anymore, whether it’s deep learning or live comedy, because we’re too focused on taking selfies and not being in the moment.”

What began as a do-or-die term of Chappelle’s appearance at various Colorado venues — including the 9,500-seat Red Rocks Amphitheatre in July — has evolved into an unexpected school pilot program, with educators learning about the service from attending Comedy Works shows, and Yondr supplying the smartphone-sized, neoprene bags and the locking/unlocking tools that comprise the relatively straightforward system.

“After seeing how it worked, I thought, ‘Oh, my God, I need this for my classroom,’ but I obviously couldn’t text or call anyone about it until the show was over,” said Broomfield High School chemistry teacher Kay Davidson, who first saw Yondr in action in July at a Comedy Works show headlined by Broomfield grad Chris Charpentier.

“I’ve been a teacher for 16 years, so to see this movement from not having any technology in the classroom to having clickers, cellphones, laptops and tablets has been a big change,” she said. “I need help managing all the distractions.”

Yondr works the same way at comedy shows as it does in the classroom: The phone fits snugly into a small bag that locks at the top, and only the teacher (or, in the case of a performance, usher) has the unlocking key. The cellphone’s owner gets to keep the bag and turn their phone to vibrate mode to know whether someone is trying to contact them.

Despite the roughly 250,000 Yondr bags in use across North America — including at more than 400 schools in 44 states, according to the company — the novel nature of Yondr makes it a gamble for some educators.

What works at a comedy or music show doesn’t always make sense for an educational setting, teachers say. And furthermore, having unfettered access to cellphone could be crucial in the case of a school shooting or other emergencies.

“We’re not shutting off or taking away phones, we’re just setting an expectation,” said Vista Peak Prep’s Rosa, who handed out three bags to each of his 60 teachers for use among the school’s 1,500 students. “It’s only an intervention tool for those who don’t follow expectations. So if a school shooting or something happened, it’s not every student who has a locked phone. And if we had an emerging situation, you could get access to your kids immediately through the main office.”

But it’s still an experiment, Rosa said.

“It could create a safety concern, or it might not work the way we want,” he said. “I don’t want to burn relationships with our students, but we do want to teach them a discipline that will help them in their lives.”

Only about a half-dozen schools in the metro area are using — or have tried — Yondr as a service so far. Strive Prep’s Smart Academy in Denver, for example, purchased a handful of the phone cases for students for use during the 2016-17 school year, but opted not to continue using them this year.

“It just wasn’t something they felt was necessary to use again,” Strive spokeswoman Chyrise Harris said.

Other schools are excited about the possibilities of Yondr and are counting on giving teachers wide leeway on how to use them, whether as a deterrent that is dangled at the beginning of class or as a matter of course upon entering the room. Either way, the fact that kids get to keep the phones removes a measure of liability from the teacher or the school district.

“We might use them for kids during field trips, but really do not know,” said Ryan Kockler, principal of Montclair School of Academics and Enrichment, which is testing 30 Yondr bags this year.

Yondr CEO and founder Graham Dugoni said his company — which is mostly rental-based — is simply a facilitator. It’s up to the people who lease or purchase the bags as to how they want to use them.

“The cases are form-fitting and as soon as the phone goes into the case, two flaps at the top close and they’re locked,” he said. “The only way to unlock it is by tapping the case with one of the unlocking tools. It’s been constructed so they’re quick and easy to use, but also don’t block people’s signals.”

If a student is waiting to hear from a parent, or a parent from a babysitter at a concert, they could simply set their phone to vibrate and have it unlocked once that happens, Dugoni said.

Educators at the metro-area schools piloting Yondr said it is paid for with nontaxpayer classroom fees, or facility fees earned by renting building space, for example, for community sports functions.

While Comedy Works’ Curtis spent about $10,000 on purchasing Yondr bags and unlocking devices for her clubs, the company usually cuts deals with schools. A bulk order may place the cost closer to $20 per bag to purchase, or $2 per unit per day to rent.

Either way, the blissful calm that falls over an environment free of cellphones feels like a breath of fresh air, according to the teachers, comics and audience members who have experienced it. Much like banning cigarettes at comedy clubs — another fidgety and ultimately unhealthy addiction.

“I’ve seen people get really upset about (Yondr) and hear more and more people lying about needing to have their phones during shows,” said comic Christie Buchele, who performs at Comedy Works. “But even if people are lying, it has the intended effect, which is to force them to think about the habitual, mindless need to stare at their phones. I mean, I do it. Everybody does it.”