About 20% of teens are considered purposeful; having a parent, teacher or friend as a role model is important

Teens with a sense of purpose do better in school, are more resilientand healthier. They are also a minority.

About 20% of teens are considered purposeful, which means they have identified something that really matters to them and are doing something about it. Joel Hartmann, a 14-year-old in Shepherdstown, W.Va., is among them.

Mr. Hartmann volunteers at Good Shepherd Interfaith Volunteer Caregivers, doing things like delivering Christmas gifts to older adults who live alone to help meet his school community-service requirements. He is close to his grandparents, and his grandmother lives with his family. “I know I would want someone to help them if they needed it,” he says. For another project, he plans on working for housing nonprofit Habitat for Humanity to combine his interest in building and woodworking and helping others.

“I’ve always loved to be around people and help them get what they need,” he says. “It gives you a really good feeling.” His parents, he says, are active community volunteers. “I learn from them.”

Mr. Hartmann is doing something that is meaningful to him and helps others. It is also something he wants to continue doing throughout his life. That is what purpose is all about, say experts.

Purpose is a particular kind of goal, says William Damon, director of the Center on Adolescence at Stanford University and author of “The Path to Purpose: How Young People Find Their Calling in Life.”

It doesn’t have to be heroic. Regularly shoveling an older neighbor’s walk when it snows for free is a small, purposeful act that helps someone in need. Making honor roll, being starting pitcher for the high-school baseball team or landing the lead in a school play are admirable goals, but they aren’t necessarily purposeful. Playing the piano can turn from a personal passion to a purpose when it benefits others.

Developing a sense of purpose is one of the most important but overlooked aspects of adolescent development, according to Dr. Damon. Many teens, while doing well enough in school and staying out of trouble, have little direction, he says.

Based on his survey of 1,200 Americans ages 12 to 26 that was published in 2008, he found that teens fall into four categories. About 25% are disengaged. They are interested in having fun and making friends. When asked to define a good life, they respond that it is doing things to make them happy. Dreamers are the 25% who think about purpose, care about things like the environment but don’t do anything about it or try to find ways to do something. Dabblers, the largest group at 30%, are those who get involved in a few causes but don’t follow through.

Only one out of five is purposeful. Among them are teens passionate about teaching history and becoming a missionary and taking steps to do so. Some are raising money to provide clean drinking water for families in Africa and others are involved in civic causes, like nonviolence.

“No two people have the same purpose,” Dr. Damon says, and purpose can evolve through life depending on new life experiences. What each had in common, though, was a parent, teacher or friend, as a role model.

As young boys, New Jersey twins Max and Jake Klein, 15, liked to spend Sunday afternoons at the home of a neighbor, who was a retired chef, and help him in the kitchen. They discovered that the man was preparing food for a homeless shelter. The boys, curious and then eager 7-year-olds, wanted to come along and serve food but found they were too young.

Disappointed, they talked with their parents. Together, they came up with ways to raise money and collect food for shelters, asking friends and family to bring canned goods or donations, rather than gifts, to their birthday parties and for Hanukkah and Christmas. As part of their bar mitzvah project, they created a website called Kids That Do Good listing volunteer opportunities for children based on age, interest and location. “Our parents taught us that we were blessed to have what we have and to find ways to give back,” says Jake.

Often teens don’t think about purpose until they have to apply to college and write an essay, says Kendall Bronk, a developmental psychologist at Claremont Graduate University and head of the Adolescent Moral Development lab. She wants to change that and has developed online tool kits, the Fostering Purpose Project, with three 15-minute activities to be completed on three different days, to help teens think about their strengths, their values, and how they can use their skills to practice those values.

In one exercise, they send emails to five adults outside the family—coaches, teachers, employers—and ask them to take 5 minutes or less to describe what the teen is particularly good at. “Trusted adults in their lives can help them think things through,” she says. They watch a short video of comedian and television host Jimmy Fallon, who learned at a young age that he wanted to make people laugh.

Schools can play a big role, says Randal Lutz, superintendent at Baldwin Whitehall School district in Pittsburgh. The high school sponsors the local Special Olympics Summer Games and encourages community-service projects. At the end of their senior year, students spend 45 minutes being interviewed by a panel of adults. Although much of the focus is on careers, they always begin with questions about the student. “How often do we take a step back from content, like English and math, and just say let’s talk about you. What makes you you?” says Dr. Lutz. “Maybe we wait too long.”

Many children, he says, are more engaged in less meaningful things, which he suspects reflects the impact of social media. That, he says, is what makes Mikayla Davic’s efforts all the more “heartwarming.”

Ms. Davic, a junior at Baldwin High School, wrote, produced and directed her first musical “A Not-So-Magical Story” in eighth grade as part of a gifted student program. She donated ticket and concession sales to Make-A-Wish Foundation because she wanted to help children dealing with serious illnesses. It was so rewarding, she produced four more shows, the latest being “Misfits,” a story of a 17-year-old California girl who runs away from home and goes to the Woodstock Music Festival. She has raised more than $45,000 and expects to surpass her goal of $50,000 by graduation.

Ms. Davic receives letters describing the Make-A-Wish children and the trips and adventures they have experienced with the proceeds from her musicals. She calls them humbling. “It changed me. Before I did this, I was just another kid who took what I had for granted,” she says. “I began to see how lucky I was and it’s motivated me even more.”