“If that boy were an apple, he’d be a Delicious!” coos a smitten, female student as Zac Efron’s teen dreamboat struts through the hallways of 17 Again.

For the next hour-and-a-half, Burr Steers’s body-swap comedy bows down at the altar of the High School Musical pin-up as he single-handedly teaches the young people of the world how to behave with dignity.

Thirty-seven year-old Mike O’Donnell (Perry) feels like he has been dealt successively bad hands by fate, with no end in sight to his misery.

His wife Scarlett (Mann) has thrown him out, his children Maggie (Trachtenberg) and Alex (Knight) despise him and, to add insult to injury, he has just been passed over for promotion at work.

In a freakish twist, Mike tumbles over a bridge into a whirlpool and is magically transformed into his 17-year-old self (Efron).

Soon the plot fast-forwards to the present day and a simple premise borrowed wholesale from It’s A Wonderful Life. Efron carries the film with his natural charm, supported by a sporadically amusing Lennon as the elvish-literate geek Screenwriter Jason Filardi keeps everything wholesome.