KATY PERRY’s been lugging around some excess baggage for a long time – childhood pals say she was so top-heavy she wore two bras to school!

In fact, one of the “Wide Awake” singer’s best friends from middle school, the Santa Barbara Christian School in California, recalled: “One time she changed for gym in the girl’s locker room. When she took off her shirt, she had not one, but two bras on, and she said, ‘My boobs are so massive, I have to wear two bras at once.’

“She was really proud and got lots of attention from the boys, which she loved. She was such a fun person to be around, full of mischief.”

The containment problem apparently continued through her years at Dos Pueblos High School.

“I remember she used to need two bras when she was at school,” said former pal Tyler Geck.

Katy, 28, has admitted she used ALL her assets to her advantage when she was trying to make it as a gospel singer in Nashville.

In a 2004 interview, she recalled how people would comment on her unusual rise to success in music circles by saying: “A total unknown working with the biggest names, Perry must have talent to burn.”

Then Katy added: “No, I’ve just got really big boobs. And my sweater gets tighter every week!”

School friends recall the bubbly brunette as a mischief-maker – despite her strict upbringing. Her parents, Keith and Mary Hudson, who were both pastors, set up the Christian Oasis Center in Irvine, Calif.

And the school friends – who called the future superstar “Katy Bird” – say they always had the feeling that there was something special about her.

“WE all knew she was going to be famous,” said pal Casey Crump. “You were always like, ‘Katy, when are you going to be famous?’”

Becky Curry agreed, noting that Katy marched to the beat of her own drum.

“She’s always been really loud, outgoing, and didn’t ever get embarrassed – no matter how embarrassed she should be!”