More than one in five school staff have had a false allegation made against them by a pupil, according to a survey.
A further 7% said they have been wrongly accused by a student's parent or family member, the poll by the Association of Teachers and Lecturers (ATL) found.
The union says the problem is putting added stress onto education workers and causing some to consider leaving the profession altogether.
Of the school staff surveyed who said they had faced an untrue allegation, 69.5% said the claim was supposed to have taken place when they were working with a class or group of children.
Others said that incidents were alleged to have occurred in places such as in one-to-one sessions in school or college, on a trip, or somewhere unrelated to the school or college environment.
Some 2.1% said the alleged incident had taken place on social media.
A teacher from the South East told the union: "My late husband was falsely accused by a child he taught. Though the Crown Prosecution Service held that there was no case to answer, he was a broken man. He returned to work briefly, but had lost his nerve.
"The false accusation of one child, who was in an abusive home situation, wrecked our family life. My husband died of a sudden heart attack in his 50s."
And a Kent primary school teacher said: "The increasing occurrence of allegations is one reason why I will be leaving the profession sooner than I would like to. Poor parental discipline is leading to children always wanting their way.
"Unable to discipline children without a comeback has meant this sort of incident will escalate and very good teachers will be driven out when they are most needed."
The ATL's branch secretary in Cornwall, David Guiterman, is proposing a resolution at the union's annual conference in Liverpool next week on this issue.
The motion calls on the union to investigate whether local safeguarding children's boards are fulfilling their purpose and whether they are doing so in a reasonable time.
A Department for Education spokesman said: "We recognise the extreme damage which can be caused to teachers who have false allegations made against them, which is why we have made clear to schools and colleges that staff should be supported throughout, and are able to return to focusing their energies on teaching as swiftly as possible."
:: The survey questioned 685 members working in schools and colleges in England, Wales and Northern Ireland between 19 February and 10 March.
