Children as young as seven have been caught sexting by their teachers, with more than half of all school staff in the UK aware of pupils using social media to share sexual messages, pictures and videos.
A study by the NASUWT union also found half its members discovered negative or abusive comments about them on social media - including posting doctored images to make them look like Islamic State ringleader Jihadi John, being falsely called a paedophile, and receiving rape threats.
Almost one-third (31%) saw a photo or video of them taken without consent, while almost one-tenth (9%) experienced threatening behaviour.
The survey also revealed pupils used Facebook to get in contact with 60% of NASUWT members, while 15% used Twitter to send them a message.
One-third of teachers said they did not report the personal abuse, with half of them saying they feared nothing could be done.
Chris Keates, general secretary of NASUWT, said: "Over the three years the NASUWT has been running this survey the situation has deteriorated.
"Online abuse has a devastating impact on teachers' and pupils' lives and yet no serious action is taken by Government to ensure that schools are responding appropriately to this abuse.
"There are still too many cases where no appropriate action is taken when abuse is reported to headteachers, the police or the social networks themselves.
"The level of abuse that teachers are suffering at the hands of parents online is simply unacceptable. How can pupils be expected to use social media sensibly and safely when parents are using it inappropriately?
"Online abuse is traumatic and potentially life changing. Victims need strong support through a zero-tolerance approach."
Just over half of all teachers quizzed said they were aware of pupils using social media to send insulting or bullying messages of a sexist nature to other students, while 53% were aware of messages of a homophobic nature and half of teachers were aware of racist messages.
Some 63% of teachers said they were aware of 14-year-olds sexting, while 45% said those involved were aged 13.
A handful of teachers said seven-, eight-, and nine-year-olds were all involved.
Examples of offensive comments from pupils, and parents, shared online include:
:: A fake Twitter account set up by pupils describing the teacher as a wife beater
:: A song posted by pupils which suggested their teacher had an affair at school
:: A Facebook group set up by pupils specifically to mock the teacher's appearance
:: Multiple threats from parents to "knock out" or "sort out" the teacher
:: A comment that the teacher was "unsuitable to work with children and deserved the sack", engaging in a campaign with other parents to try to make it happen.
The Department for Education said: "Young people and teachers should be able to take advantage of the vast potential that the internet and social media offers to their lives and education. But they also have a right to feel safe.
"We want to make sure young people are aware of the risks and dangers - including sending inappropriate images. That's why schools should deliver high quality PSHE (personal, social, health and economic) which is an important opportunity to teach young people about how to stay safe and avoid risks.
"To support schools to do that we have funded and produced a range of guidance and support on issues ranging from consent to internet safety. The law is also crystal clear that where teachers find indecent images of children they must report this to the police.
"No teacher should be subjected to abuse or threatened online. Where teachers are, we would urge them to report it to the relevant authority so the appropriate action can be taken."