It was in a public place. There is no expectation for privacy. The bully was not whispering. He and the other teens were talking loudly for the whole class. "According to Love, as the teacher is heard attempting to help her son with a math problem, a student says, “You should pull his pants down!” Another student replies, “No, man. Imagine how bad that (c**t) smells! No one wants to smell that (t**t).” As the recording continues, the teacher instructs the classroom that they may only talk if it pertains to math. Shortly thereafter, a loud noise is heard on the recording, which her son explained was a book being slammed down next to him after a student pretended to hit him in the head with it. When the teacher yells, the student exclaims, “What? I was just trying to scare him!” A group of boys are heard laughing."
What privacy is expected when you are trying to make a spectacle to an entire classroom? As well this was done in a public building. During public hours.
As well I'm pretty sure that building was riddled with security cameras.