Three-quarters of Welsh schools failed to respond to ministerial and researchers' requests for copies of their anti-bullying policies, says a new report.
The level of returns was "disappointing", according to a team from Cardiff university, which was commissioned by the Assembly government to evaluate schools' policies.
In follow-up calls, some schools said they had not responded because of "pressure of work and the relative level of priority assigned to the request".
Response rates ranged from 62 per cent of schools in Monmouthshire, to only 8 per cent of those in Gwynedd.
However, after two letters - one from education, lifelong learning and skills minister Jane Davidson - and other follow-ups, policies were received from all 227 secondary schools in Wales.
But unions say heads are swamped by requests for information, often from government officials, for data that has already been supplied.
Dr Philip Dixon, director of the Association of Teachers and Lecturers Cymru, said: "Most schools are concerned that there should be no bullying.
But they have so many requests for information that this was perhaps seen as just another one. The Assembly government needs to think about the workload put on schools."
The full evaluation confirms previous preliminary findings (TES Cymru, October 21) that a third of schools' anti-bullying policies are not up to scratch.
The report is critical of those that have adopted "off-the-shelf" policies without adapting them or consulting with children, staff and parents.
But even the best schools are not monitoring and reviewing the impact of their policies, says the team, which evaluated 480 school policies against Respecting Others - the Assembly government guidance on tackling and preventing bullying, sent out in 2003.
All schools in Wales are legally required to have a written anti-bullying policy. The research found some had been included as part of general behaviour policies.