PUKALANI, Maui — Grammy-nominated musician Jack Johnson, just back from a tour of Europe and Japan, usually doesn't perform in school cafeterias. But there he was yesterday, serenading Pukalani Elementary students with "The 3 R's," a song that urges children to "reduce, reuse and recycle."

The singer-songwriter has earned a new, younger fan base with the recent release of his "Sing-A-Longs & Lullabies" album from the "Curious George" movie, which debuted atop the Billboard magazine sales chart. But kids can be a tough audience.

"Sometimes it's just blank stares and they're just watching," said Johnson, who visited the Maui campus on behalf of his Kokua Hawai'i Foundation, which supports environmental education in the schools.

The resident of O'ahu's North Shore said he didn't set out to cross over from folk rock to children's music. "I was just going to write one song for the movie and the next thing I know I had a kids' album," he said.

Most of the Pukalani students didn't appear to recognize Johnson until he sang the "Upside Down" song from "Curious George."

Afterward, they all lined up for autographs as he graciously posed for photos and signed each scrap of paper that was thrust at him. His appearance had been kept a secret to prevent the school from being mobbed by grown-up fans, and the adults who did show up giddily waited their turn to meet the star.

Fourth-grader Noah Murayama said he listens to Johnson's music "all the time in the car." The excited 9-year-old asked the singer to sign his right arm. "I was showing everybody at school," he said. "I'm not going to wash my arm."

The miniconcert by Johnson was one of the prizes awarded to Pukalani Elementary for being the island winner of the "Cash for Cans Challenge." The 470 students collected more than 7,000 cans during the two-day contest, and also received $1,000 from Reynolds Recycling. Other contest sponsors are Honolulu-Ball Corp., Horizon Lines and Castle & Cooke Hawai'i.

The second-place Maui school was Christ The King in Kahului, which received a $500 prize.

Winning schools on Kaua'i and O'ahu also will receive a visit from Johnson.

"When we realized we'd won, it was a real delight. I think the staff was more excited about it than the students," said Pukalani Elementary Principal Chad Okamoto. "It was nice for us, too, because we don't get many musical opportunities."

School counselor Jim Flavin organized the can-collecting campaign, making signs and take-home fliers, and lining up prizes for the students who brought in the most cans. The winners were fifth-grader Mackelan Mitchell and first-graders Keegan Gregg and Keanu Hussey.

While Johnson was at Pukalani Elementary to promote recycling, he did offer the children some advice about songwriting. Johnson said he often sings about growing up in Hawai'i and other personal experiences.

"If you want to write a song, just sit down and start writing little rhymes about things that you do every day," he said.

Johnson appeared last night at a sold-out Kokua Festival concert at the Maui Arts & Cultural Center, and will perform another sold-out concert Saturday at the Waikiki Shell.

Both events benefit the Kokua Hawai'i Foundation, started by Johnson nearly three years ago. The nonprofit group worked with O'ahu Community Recycling to establish a 3 R's recycling program at 10 schools, offers grants to teachers for environmental field trips and is sponsoring a couple of environment-themed plays for children.

This fall, the foundation will kick off a "Farm-to-School" pilot program at five O'ahu elementary schools: Sunset Beach, Wai'alae, Moanalua, 'Aikahi and Wheeler. Johnson said the program will set up gardens at the schools and teach children about organic farming, composting and nutrition, with fresh produce and salad bars incorporated into lunch menus.

Reach Christie Wilson at cwilson@honoluluadvertiser.com.