People around the world were shocked and horrified by a viral video that showed Karen Klein, a 68-year-old public school bus monitor, desperately trying to ignore malicious verbal jabs by a group of middle schoolers on her own bus.
For most, it was extreme. For many educators and school staff members, it's no surprise. School workers said it's a regular aspect of their daily lives.
"I've had erasers thrown at me, among other things, but these are things that teachers go through," said Rosalind Wiseman, author of the bestseller "Queen Bees and Wannabes."
"When these types of things come up, there's all of this attention. But most teachers have at least had one student call them a bad name under their breath."
While bullying among students has dominated conversations in school, homes and in the media, kids bullying adults at school is a topic rarely discussed. What some call misbehavior, pranks or insubordination can be bullying, too, educators said. Kids can act threateningly and create a hostile environment inside the limitations of the law, said educator and author David M. Hall, who often leads anti-bullying workshops - and school workers might never report it.
"Schools often forget about the adults," said Jessie Klein, author of "The Bully Society: School Shootings and the Crisis of Bullying America's Schools." "People are so resigned to it. It's almost invisible - it's just the way things are. Kids can't imagine what a school would look like without bullying, so teachers are resigned to it, too."
Severe incidents, such as shootings, become part of police statistics. But there aren't many numbers about kids bullying adults, according to Tom Lansworth, media affairs specialist for the American Federation of Teachers. Most school districts aren't required to track incidents, he said. The Canadian Teachers Federation conducted a study in 2005 that found one-third of teachers in Ontario had been bullied by students. Part-time teachers and those without regular grade assignments were most likely to experience bullying, the study found.
Some educators said bullying incidents aren't taken seriously by administrators, and school workers without unions might be discouraged from acting. Educators might be discouraged from reporting bullying because it could hurt the image of the school, or make them appear ineffective in their jobs, teachers said.
"I think it's very difficult for teachers to report to their administrators that their kids are being disrespectful," said Wiseman, who is also a parent educator. "It's shameful for teachers to admit that, because you're admitting that you don't have any control over the kids. It's embarrassing."
Teachers CNN talked with shared stories ranging from thrown erasers to verbal threats. Students are known to key teachers' cars or deflate their tires, said Lansworth, the American Federation of Teachers spokesman. He's heard about students who steal teachers' property; cyber-bully teachers by creating fake Facebook pages or postings; push teachers to snap, and capture teachers' responses on camera.
"We're supposed to be strong," said teacher Hall. "It's the same embarrassment that kids feel."
Just as students can create hostile environments for each other, they can do the same toward teachers, school janitors or cafeteria staff, Hall said. He said he worked with a Jewish teacher who felt intimidated by a student who professed to be a neo-Nazi. The student, he said, would insist on reading Adolf Hitler's "Mein Kampf" in the teacher's study hall periods.
"A kid may not be doing anything he can't do, but he's using his rights to extend intimidation against a teacher," Hall said.
Outside the view of principals and parents, workers who aren't perceived to have power in school communities -- bus monitors, for example -- are often targets, educators said.
"If there are children who feel empowered to abuse somebody that they see as weaker, then it can happen that those children would go after an adult, especially someone that they see as someone without any authority," Wiseman said.
Some educators said bullying is a matter of perspective; they draw a line between bad behavior and bullying at different points.
Elizabeth Jordan, a middle school teacher from California, said it's important to remember that kids have their own struggles, too -- few coping tools, rapidly changing bodies and bullies of their own.
"It's just sort of an epidemic of the age that I teach, that the kids can be very angry," Jordan said. "You're going to find that the common thought everywhere is that they should get shipped out to an island for three years and they'll come back as normal human beings. But you have to have a certain attitude when you teach middle school. I try to keep a sense of humor."
When children cross "lines of respect" with peers and teachers at early ages, it's misbehavior, said Ana Messinger, a fourth-grade teacher from South Carolina. As they get older, students figure out what they can and cannot get away with -- and who will tolerate such behavior.
"When it becomes consistently directed at another, it's bullying," Messinger said. "I have seen incidences that have crossed the line of respect, of empathy for other people, absolutely."
Messinger said it's important for everyone in a school, not just the administration, to be vigilant in this regard.
"Student-on-student, student-on-teacher, teacher-on-student bullying? They each feed each other," she said. "Teachers need to be diligent about documentation and communication with parents and children and within school buildings so that everybody is on the same page, so that when those lines are crossed we can respond appropriately and swiftly. Otherwise, the administration is just going on the teachers' words."
Thousands of schools, including Messinger's, are adapting programs like Positive Behavioral Interventions & Supports, which works to improve learning environments and reward positive behavior. The program isn't perfect, she said - a lack of negative consequences leaves boundaries incompletely defined, and it focuses on bullying between students. But the program has helped to shape a curriculum that highlights respect, effort, attitude, cooperation and honesty, she said.
Messinger said that programs focusing on respectful interaction can help "reteach" not just students about how to handle bullying interactions, but teachers as well.
"It's a vicious cycle," she said. "There's no one culprit to this. I can't say it's so-and-so's fault. It's in society -- it's in the house, it's on TV, it's in the playground. It's adult-on-adult bullying that they're watching. We've lost, as a society, our decorum when we talk to one another."