Does it count as child abuse if they were a child as well?

I'm no expert, but I'd say no. Though it's not to the same mature caliber, two seven year olds fighting at school wouldn't be called child abuse. (even if one blatantly encouraged it) The teacher will intervene, parents will be called, and if the parents a smart, there will be harsh consequences. Whether it's your situation or a school fight, the outcome will be the same. Legally, I don't think it's child abuse.