What the &#%*? Pop tart Britney Spears admits her kids have potty mouths and her 3-year-old even says the F-word!

"They're staring to learn words like 'stupid,' and Preston says the F-word now sometimes," Spears says of her boys Sean Preston, 3, and Jayden James, 2.

But Brit insists Preston didn't learn to curse from her. "He must get it from his daddy [Kevin Federline]. I say it, but not around my kids," she tells Rolling Stone.

As for her new low-key life (Dad's keeping her on a tight leash!), Britney says she feels like "an old person now. I do! I go to bed at, like, 9:30 every night, and I don't go out or anything."