Last year, Rabbi Laurie Hahn Tapper sat in on a third-grade morning meeting at Yavneh Day School in Los Gatos, where she works. The topic was self-control, and one by one, the children went around the circle and shared stories of how they had practiced or struggled with self-control. When the “talking heart” finally made its way to one little boy, he spoke with urgency and immediacy.

“I’m practicing self-control right now because I really want to put my arm on my neighbor and lay down on him,” he said, “but I know I have to sit here.” Tapper, who is the school rabbi and director of Jewish studies, recalled the exchange fondly as she spoke with J. recently, during the first week of the new academic year. “It was really heartfelt,” she said. “Once you give them the language to articulate something that feels confusing inside, they start using it.”

At Yavneh, a Jewish K-8 school, concepts like “self-control,” “perseverance” and “gratitude” are part of the curriculum. Like a growing number of schools across the country, Yavneh has elevated character development to a central part of its educational mission. Character is a core skill to be developed in students, alongside reading, science and math.

“We teach our kids how to flex their mensch muscles,” Tapper said.

In just a couple of weeks, Yavneh will join more than 50,000 schools, synagogues, churches and community organizations in 80 countries around the world on Sept. 22 for what could be considered the mensch Olympics: Character Day.

The brainchild of Mill Valley Emmy-nominated filmmaker Tiffany Shlain and now in its third year, Character Day is designed to spark conversations about character strengths and how to develop them. In the San Francisco and Oakland public schools, at San Francisco’s Congregation Emanu-El, the Contemporary Jewish Museum and thousands of other participating organizations around the country and the world, people of all ages will watch Shlain’s three short films about character and the brain, have conversations using customized discussion materials, and participate in a daylong, interactive live webcast featuring educators, psychologists and spiritual leaders.

Shlain’s nonprofit, Let it Ripple, provides all Character Day materials for free. (Multiple donors and foundations support the organization’s work.)

“There’s been all this research to back up ways of developing yourself,” said Shlain, who in her 2014 film “The Science of Character” highlighted research in the fields of neuroscience and positive psychology that suggests character traits can be fostered and reinforced through practice.

The idea is not entirely new — it’s been promoted over the centuries by thinkers as diverse as medieval Jewish mystics and Benjamin Franklin — but more recently it has been bolstered by brain research. Repetition of small simple tasks, such as giving away a dollar a day to demonstrate generosity, can actually build character strengths such as love, kindness and a sense of social responsibility. Shlain says people are hungry to learn about this yoga for the mind.

“There has been a lot of research in neuroscience that says neurons that wire together fire together” she said, referring to the idea that the brain can be rewired and character molded through simple behavioral changes. “I think morals were often talked about in temple or church. As affiliation has gone down, there was a vacuum for these conversations.”

Jews have been exploring this mind-body connection for centuries. After “The Science of Character” came out, members of the Jewish community introduced Shlain to the tradition of Mussar — a Jewish ethical practice that aims to build good character traits through careful text study and self-reflection. It was developed into a movement in the 19th century among Lithuanian Orthodox Jews but is now enjoying renewed interest among all Jewish streams (see J. cover story “Study more, be a better person — the way of Mussar,” March 2015).

Shlain was intrigued and immersed herself in learning about Mussar; it became the basis for her most recent film, “The Making of a Mensch.” The film, which premiered last year on Character Day, explores how this spiritual practice, with its origins in Jewish texts written hundreds of years ago, reflects contemporary understandings about how to change habits, behavior and character.

“The word spiritual is thrown around all the time, and sometimes it seems detached from what it means to be a spiritual, embodied person in the world,” said Rabbi Sydney Mintz of Congregation Emanu-El, who will host a “coffee and character” event for preschool families on Sept. 22 at her San Francisco synagogue. “I see Mussar as the way we can be spiritual, embodied people because it’s tied to our actions.”

Jewish schools, synagogues and JCCs can utilize Jewish-themed resources for Character Day by screening “The Making of a Mensch” and using “Mensch”-themed discussion cards that include the Hebrew word for each character quality, called the middot. The cards ask questions like, “Who in your life represents this quality and how?” and “What are other strengths or middot that you could dial up or down to help balance this quality?”

The free materials come with a poster featuring the “Periodic Table of Being a Mensch”; at Yavneh, the display hangs prominently in a school hallway. (The mainstream discussion materials have similar content minus the Hebrew.)

With Character Day happening just prior to the High Holy Days, it’s a natural time for discussions about personal growth.

“Teshuvah [repentance] is definitely about character: the kind of people we aspire to be, the kind of people we can be,” said Mintz. “I think Character Day is in the chain of tradition of getting us closer to our Jewish selves.

“People think science and religion are separate,” she added. “But I love the way [Shlain] brings all the parts of science and our brain together. It’s OK to ask spirit questions about science.”

Character Day has proven to be a popular event in both religious and secular spaces and has grown rapidly since Shlain launched it in 2014 with 1,500 participating schools and organizations. That number grew to more than 5,500 last year, and more than 50,000 participants from 80 countries signed up this year, according to the Let it Ripple website. Partners include the State Department, Common Sense Media and the Foundation for Jewish Camp. The Character Day global webcast will feature talks with luminaries including Rabbi Lord Jonathan Sacks, former chief rabbi of England, and Martin Seligman, director of the Positive Psychology Center at the University of Pennsylvania. Participants are encouraged to customize their own events, using the Character Day discussion materials, online programs and Shlain’s three films (“The Adaptable Mind,” which premiered in 2015, completes the trio).

The Contemporary Jewish Museum will screen “The Making of a Mensch” on Character Day as part of its young adult series “Night at the Jewseum.” Shlain will participate in a question-and-answer session after the screening. Gravity Goldberg, associate director of public programs at the museum, said Character Day will be a meaningful experience for young adults who are looking for ways to connect with the High Holy Days in a nontraditional way. As in previous years, the museum will feature a graffiti-friendly Atonement Wall in partnership with Reboot that invites participants to write what they wish to atone for that year.

People are “looking for ways to connect with their Jewishness, but in ways that don’t feel so like synagogue,” Goldberg said. “So Character Day, which makes you think about how to be a mensch, registers with more secular [Jews]. It’s something people really desire.”

Programming around character development has become popular among K-12 educators. Kevin Truitt, an associate superintendent in the San Francisco Unified School District, introduced Character Day to the district last year and says all San Francisco public schools will be participating in some way this year.

He was attracted to Character Day as a way to support his efforts to make school district practices less punitive and more compassionate toward minority and at-risk students.

“We’re always talking about a growth mind-set,” Truitt said, an important frame of mind for both students and teachers. If students believe they can change, it helps their self-esteem and they will be more likely to tackle challenges and do better in school. But Truitt reported that teachers frequently are guilty of bias against students whom they have labeled — even subconsciously — as low achievers.

“I think the tendency with marginalized youth is to label them with negative outcomes,” he said. “That is the fixed mind-set.”

When teachers are given the vocabulary of positive character traits and use these to describe their students, they begin to recognize the potential of everyone, according to Truitt. And for students, “It shifts the whole focus to ‘I am somebody, I can be something.’ ”

Shlain, who has spent her career studying the evolution of the internet and addressing questions raised by the use of technology in daily life, believes living in an interconnected society poses challenges while also providing opportunities.

“We’re all part of an ongoing experiment with the online world and the global society.  We’re in a place we’ve never been,” said Shlain, whose family “unplugs” for 24 hours every Shabbat. “I think refocusing on character and grounding ourselves and redefining how do you want to be online, how are you using technology, what does it mean to be present with my family — all of these questions should be asked all the time.”

Visit www.letitripple.org to find a Character Day event or sign up to participate.