There’s plenty of sweet on-screen romance between Troy Bolton and Gabriella Montez in upcoming  “High School Musical 3″.

But don’t try asking actors Zac Efron and Vanessa Hudgens to spill the beans on their  real-life romance of more than a year.

In the movie, opening in the U.S. and much of Europe next week, teen sweethearts Troy and Gabriella waltz on a rooftop garden, hold hands in a garden hammock, and gaze at the stars from a treehouse while they navigate their senior year of high school and the prospect of college in separate cities.

And that’s before they even exchange a kiss.

Yet Efron, who turns 21 on Oct. 18, and Hudgens, 19,  declined to be interviewed together during press promotions in Beverly Hills this week, and both fended off questions about their own future together.

“It’s just so much easier not talking about it. I told myself that a long time ago,” Efron said shyly of the relationship.  “Troy and Gabriella are very much like real high school kids. It’s what high school romance should be like — not too lustful.

“I’ve always said that Troy and Gabriella were best friends before being boyfriend and girlfriend,” he added.

Was that a hint?

Hudgens was even less forthcoming. Her eyes flashed , Sharpay-like, when asked if she’d take a personal question.

Told that millions of HSM fans would at least hope that she and Efron plan to stay together after three years of watching their characters fall in love, she replied only; “That’s very sweet.”