Some schools around the world have banned smartphones. Others have banned energy drinks. But here's something new that's reportedly been banned in some classrooms — numbers! That doesn't mean math lessons have stopped. The ban refers to a slang term that's gone viral this year. The term is just this: "Six-seven." That's it! Teachers across the globe say it's taking over their classrooms. Children are shouting out "six-seven" in the hallways and on the schoolyard. Does this mean kids suddenly love counting? No. Here's the story, which began toward the end of 2024. The term seems to have come from a song called "Doot Doot (6 7)," which was released in December 2024 by US rapper Skrilla. At around the same time, Taylen Kinney, a US high school basketball star with a large online following, was shown on video being asked to rate a drink out of 10. He replied: "Like a six … six … six-seven." Kinney started using the Skrilla song and the same phrase in his TikTok videos, which have been watched millions of times. In the initial clip, and in subsequent videos, Kinney made a hand gesture to accompany the term, raising and lowering his hands like old-fashioned weighing scales. Kinney has even released a clothing range with the numbers six and seven on it! So what does it actually mean? That's the big question. Gabe Dannenbring, a teacher from the US, told CNN: "Nobody knows what it means." The New York Post says it "can mean nothing, something or whatever you want it to mean." Dannenbring added: "It's like a plague — a virus that has taken over these kids' minds." That's why it's been banned in some classrooms — not because it's inappropriate, but because it's so annoying. Dannenbring said he now can't mention either number in class without students shouting out, "Six-seven!"