Not quite the same, but, my DSs were 11/13. Day time. They were endlessly verbally sparring with each other, and me, non-stop. Every request was met with aggressive belligerence.
I lost it. I can recall shouting, bellowing, at the top of my lungs, up the stairwell to the pair of them (with a tiny concern that the neighbours might hear 🤭) that this was going to STOP, RIGHT NOW, and if it didn't, I was WALKING OUT THAT DOOR AND NOT COMING BACK. I was SICK TO DEATH of the endless sniping and bickering. I'M TIRED, GOING OUT TO WORK EVERY DAY THEN COMING HOME TO DEAL WITH THIS. Just STOP!
I did reference that the elder goaded his brother relentlessly, very often in petty matters; but the younger rose to the bait, Every Single Time.
I think I used the word 'fuck' quite a lot 🤭
It was remarkably effective. They were both shocked. They discovered, that day, that their parents have boundaries, too. They don't have to wear your shit all the time.
It was cathartic, typing that.
They're now 25/23 and wonderful young men.
But no one needs to put up with poor behaviour from secondary schoolers.