Every Friday at 10 a.m., Demetra Williamson skips her math class at North High School, jumps into a taxi and, for about 40 minutes, transforms from student to teacher.

"How old do you have to be to be a grown-up?" 15-year-old Demetra asks a group of fidgety but admirably polite first-graders, seated on the floor of the Nellie Stone Johnson Community School gym in Minneapolis.

Hands shoot up. "Twenty-one!"

"What can hurt your growing brains and bodies?" she continues.

"Bad foods," says one student. "Eating shampoo," suggests another. Demetra laughs. "Yes, eating shampoo is not good." Cigarettes, alcohol and adult medicine are not good, either, she tells them. "Those can hurt adults, too, but they hurt children more," she said, "because their brains and bodies are still growing."

Demetra, a North High junior, is a peer leader with Protecting You/Protecting Me (PYPM), an alcohol use prevention program developed by MADD and Hazelden. It builds confidence and awareness among first- through fifth-graders, helping them make smart and safe decisions later on. Early results are good.

But one of the sweetest outcomes is the confidence and awareness PYPM is building in its young teachers -- the kind of students who often fall under their high school radar.

"They're not the great athletes, they're not in student council or band, their grades are average," said North High health educator and PYPM trainer Brenda Corbin. "But they're honest. They have integrity."

Exactly the kind of leaders she wants. All she has to do is convince them. "Sometimes, I literally pull them into this program," she said. "All of a sudden, they have a role to play and they are good at it and they can tell they're good at it. That brings about the possibility of 'Maybe I'll be a teacher,' or 'I can go to college.'"

Corbin, who has taught at North for 23 years, was bullish on PYPM from the start. Too many prevention curriculums, "with a story of two-parent families and upper-middle-class values," are a miss for her community of kids, Corbin said. "We're very used to tweaking this and that."

PYPM didn't require tweaking. The lesson plans and materials, which include age-appropriate information about brain development, friends, choices and laws, come with illustrations of kids who look like Corbin's students. Their enthusiastic young teachers look like them, too, and understand their challenges.

"These are kids of poverty," Corbin said of her peer leaders. "It's just amazing to me that they are the first people to step forward and say, 'I want to help.'"

Corbin started with about eight high school students five years ago. By the next semester, 30 kids signed up. Today, she has to turn away about 20 kids every semester. "I say 'Try again,' and I try to pick them the next time around."

Peer leaders receive two weeks of intense training, learning about the effects of alcohol on the brain. Corbin also teaches them how to ask good questions and keep the small fry on task.

The Friday morning sessions run like clockwork. The first group of five North High students teaches fourth-graders from 9 to 10 a.m., then makes way for Demetra's group. As her group heads back to school, another team of five arrives via taxi to work with third-graders.

Corbin said it's not unusual for them to innovate as they go. "They'll say, 'We added this, is that OK? Can we do a poster?' They're always looking for ways to make the lesson even better."

PYPM has been running nationwide for about a decade, with good results. Retention of information from year to year is high, with big jumps in knowledge about alcohol's effects on the brain. Participants also report much higher rates of refusal to ride in a car with a driver who has been drinking.

The results thrill Mike Conley, who supports PYPM through the Conley Family Foundation. Conley, chairman of the Hazelden board in the early 2000s, attended North High, as did his wife, Sharon. Their foundation focuses on innovative ideas rooted on the North Side.

"When I look at the results, such as students staying in school and raising their GPAs, it does my heart good," Conley said.

South and Roosevelt high schools added the program last year. The goal is to offer it in every Minneapolis high school, said Hazelden spokeswoman Marty Harding.

The eight-week program ends with a party. Youngsters are awarded a certificate and their teachers are presented with sweatpants and hoodies that they design themselves. The teachers also receive school credit and community service hours, which they proudly add to their college portfolios.

Demetra is considering becoming a teacher or maybe a singer. Either way, she said, this experience has transformed her.

"I am definitely planning on going to college."

gail.rosenblum@startribune.com 612-673-7350