All the girls think he’s dreamy — and for once, their mothers don’t mind.

Clean-scrubbed “High School Musical” heartthrob Zac Efron, who grew up in San Luis Obispo and Arroyo Grande, Calif., in a non-showbiz family (his father is an engineer), began acting at 11 after his parents encouraged him to audition for school theater productions. His natural talent and singing chops soon got him roles in productions of “Gypsy,” “Peter Pan,” “Mame,” “Little Shop of Horrors” and “The Music Man.” He also won more dramatic parts in “ER” and “The Guardian,” and then in 2004 joined the regular cast of “Summerland” after several guest appearances. This summer, the 19-year-old “HSM” star and two-time Teen Choice Award winner debuted on the bigscreen in “Hairspray.”

“He’s ambitious and so talented, yet very self-effacing — just like Cameron Diaz,” says “Hairspray” director Adam Shankman. “He doesn’t care about being cute or cool. When we shot (the song) ‘Without Love,’ I made him make out with a photo of Nikki Blonsky for over two hours. I tortured him, and he was great about it.”

“I cast him because we just couldn’t let him go,” agrees “HSM” director Kenny Ortega. “We’d pared it down to 40 kids, and the audition went on for hours, like an old Broadway audition, and whatever I threw at him — improvs, singing, dancing or athletics — he did. I couldn’t wear him down. We’d pair all the kids up differently, and it quickly became clear that Zac and Vanessa (Hudgens) had this real chemistry.”

An admitted “nerd” and straight -A student, Efron had already been accepted by USC by the time he signed on to do “HSM,” but he deferred enrollment. For now, he’s focused on his career and set to star in another musical, a remake of the ’80s hit “Footloose.”

But Shankman cautions that Efron “probably should back away from musicals for a while now. The best thing he could do is more drama or a comedy and cultivate a male audience. It’s always tough when your audience is so heavily skewed in one direction.”

Recent breakthrough: “High School Musical” and “Hairspray,” his first feature film

Role model: He’s always idolized “Hairspray” co-star John Travolta since seeing him in “Grease.” Travolta made musicals “cool” for him.

What’s next: “Seventeen,” in which he plays an adult who wakes up one day as a hunky high schooler.