Government plans to collect details of all abusive incidents in schools could create a bullying "league table", unions have warned.
Publicly available data on the number of attacks on staff and pupils could lead to primaries and secondaries being stigmatised and a new "blame culture", according to the NUT and the NASUWT.
In future, teachers will have to report all serious and persistent cases of bullying to the Department for Children, Schools and Families and their local authority.
The DCSF says the changes will keep schools safer and make teachers review anti-bullying policies. But teaching unions are concerned officials will use the data to judge schools and hold them to account.
Ofsted inspectors will also be able to view the figures and the DCSF will use them to produce reports on regional and national trends. They might also be available to members of the public who requested them via the Freedom of Information Act.
Chris Keates, general secretary of the NASUWT, said teachers might not feel safe recording incidents.
"It is important that such data is not used to create league tables of schools or to contribute to a blame culture in which individual schools may be penalised," she said.
The bullying figures would be recorded on software in development, and given to parents.
The DCSF has promised this will not be a "bureaucratic burden" on teachers. Incidents will be listed by "specific form of prejudice" - for example race, religion or culture.
Both the NUT and NASUWT are calling on the Government to make sure schools have anonymity when the figures are released.
John Bangs, head of education at the NUT, said: "It is the schools which submit a nil response to their local authority which constitute a problem, and which require support.
"Higher reporting levels does not mean a higher incidence of bullying behaviours, it means that teachers have been focused on tracking bullying."
Many schools already record serious incidents but do not have to submit them to local or national politicians. Both unions said teachers under-reported because they did not want to be seen as having a "bullying problem". They want basic data only to be given to local authorities and the Government, but all incidents - not just the most serious - to be recorded.
DCSF guidance on the changes says: "We have no intention to produce bullying 'league tables' or any similar comparative tables. In some cases, schools with high returns of bullying statistics are actually those with more effective and proactive anti-bullying policies."
Bully for them
About half of all children aged between 12 and 17 say they have experienced some type of bullying.
- Poor, white children are most likely to be victims of bullying.
- Sixty-one per cent of white pupils have admitted to being bullied, compared with 32 per cent from ethnic minorities.
- Around four in ten children from the richest "ABC1" homes said they had been bullied, compared with 57 per cent from the poorest "E" households.
- Teasing and name-calling is the most common form of abuse, peaking between the ages of five and 11.
Source: research published last month by the Department for Children, Schools and Families.