The slogan on the bracelet says "I heart boobies."
Officials at Rocklin High School asked Cooper to hand over the bracelet for the day, and had him choose between Saturday school or suspension.
"I was surprised because I was just like, wow, there's not a good reason for me to take it off," said Cooper.
Cooper's mother said she liked the slogan because it was different, but school officials said it is not appropriate.
"If it says 'I love boobies,' yeah, it's inappropriate for school," said the principal of the school.
The Coopers said they plan to appeal the punishment if the superintendent doesn't rescind it.