“When you’re unkind to another, it’s usually about ourselves and how we are feeling,” she said. “If children can take a moment and just breathe, they can avoid acting out against others.”

There appear to be other benefits. Research led by the clinical psychologist Lisa Flook has shown that youngsters who received the kindness training become more altruistic in tests that measured their willingness to share with others. It also strengthened children’s ability to focus and modestly boosted their academic performance.

Some argue that emotional skills are better taught by parents than by teachers. But Dr. Flook points out that when kids come to the classroom anxious, angry or fearful, they are often too distracted to focus. “Children who have positive relationships with their peers and teachers do better in school,” she said.

They may also fare better later in life. One 2015 study that tracked kindergartners to young adulthood found that individuals with good prosocial skills — behavior that is positive, helpful and friendly — tended to be more successful as adults than those who did well in subjects like reading and math but lacked the ability to get along with others.

The Kindness Curriculum is part of a growing global movement to teach emotional intelligence in schools. Advocates of this approach say it’s shortsighted for teachers to focus narrowly on intellectual learning and ignore the cooperative emotional skills that enable learning — and learners — to flourish.

Still, some question whether personality traits like kindness can be taught.

Richard Davidson, the founder of the Center for Healthy Minds, believes that ancient Buddhist wisdom provides clues. He was inspired, he said, by a request from Tibet’s spiritual leader, the Dalai Lama, who asked him to take insights from contemplative practice out of their religious context and use them to develop strategies to help improve people’s lives.