On the carefully manicured lawn at Loreto Mandeville Hall Catholic girls school in Toorak, a sea of girls in white hats waited patiently for the arrival of international superstar Katy Perry.

The singer is in town for her Prismatic tour and will perform Friday night at Rod Laver Arena but on Thursday afternoon she fielded questions from the excitable students, winners of a Telstra-sponsored competition for their film clip that sung the virtues of their school and included Katy Perry lyrics.

The prize was $10,000 for their performing arts program, twenty tickets to Perry's Friday night concert and a visit from the star, resplendent in colourful silk shorts and t-shirt and a Frida Kahlo-inspired braid.

"If I could talk to my childhood self right now I'd say stop worrying about boys, they're very distracting," advised Perry, who shot to fame in 2008 with the lipstick lesbian anthem I Kissed A Girl.

She also implored the students to work hard, because "knowledge is power, the more you can focus on your studies, the more powerful and strong you are", told them of her favourite colours, "all the pastels, Easter colours" and inspirations - her sister, a new mother, punk pop icon Gwen Stefani, and Mexican artist Frida Kahlo.

"You should check out her art and her story, if you don't know about Frida Kahlo it's a gorgeous story about strength and perseverance and beauty, and finding beauty even in all the pain she went through," said Perry.

One student asked Perry, 30, what her favourite age was.

"There's a lot of change that happens in your 30s, a lot of maturing and a lot of not really caring what anyone thinks about you, just caring about what you think about yourself," Perry said. "That being said, I liked my metabolism at 23, I liked 23, around that age because you're a little bit more invisible, you've got a little more collagen -- you'll know what that means later on in life."

The four students who appeared in the winning video led a percussion ensemble in another song welcoming Perry, and assembled on stage for a photo with their idol.

"She told her what shampoo she uses so now I'm going to use the same one so I can smell like her," said nine-year-old Gillian McDaniel.

"She inspires me because she wears different costumes to other people, she doesn't care if she's different," said Claudia McNee, 9.

Perry praised the girls for the creativity and genuineness that came across in their winning video.

"The four girls in these uniforms they made this adorable video that seamed together the titles of my songs, and they made it in so many different ways and so many different areas, I think they used the whole school grounds to do it, and they were just so genuine about it," she said.

"I think they really liked expressing themselves and being creative with it."

Perry has sold 81 million singles and over 11 million albums. Friday night's show is the first of eight she will perform in Melbourne at Rod Laver Arena.