In return, Lambert, 27, offered the crowd at Mt. Carmel High School two songs and a few words of appreciation.
"This is so weird," he said, thanking the crowd from a makeshift stage on the packed stadium's field. He advised students to "believe in yourself" no matter what others may say.
His entrance - in a cherry-red convertible - was heralded by the screams of cheerleaders. The marching band played as Lambert slowly cruised the stadium track, drawing shouts from the bleachers.
Lambert's renditions of Michael Jackson's "Black or White" and "Mad World" won applause despite a tinny sound system.
His "American Idol" competitors, Danny Gokey of Milwaukee and Kris Allen of Conway, Ark., were also feted by their towns Friday, with Fox taping the events to air next week on "Idol."
The winner of Fox TV's singing contest will be announced on the May 20 "American Idol" finale.
In San Diego, a woman wearing a sports bra but sans blouse rushed the stage to get closer to Lambert and was quickly hustled off. When Mayor Jerry Sanders stepped up to declare Friday "Adam Lambert Day" in San Diego, he jokingly vowed to keep his shirt on.
The stadium was draped with banners reading, "Mt. Carmel (Hearts) Adam!" and, "You're Our American Idol." A poster toted by a fan proclaimed, "Adam, You're a Rock God"
- echoing show judge Kara DioGuardi's assessment of Lambert, who has performed in musical theater.
He's been a consistent favorite with the "Idol" judges, even the tough-minded Simon Cowell.
Lambert was a standout in high school, too, said Bryan Clark, 26, of San Diego who graduated in the class of 2000 with him and attended the celebration Friday.
"He was definitely good," said Clark, who recalled seeing Lambert perform at pep rallies and other school events. "I'm proud of the guy. It's always good to see people making their dreams happen."
