Heads locked in stressful disputes with teaching staff are not getting the support they need from local authorities, say education unions.
Following widespread concern, Jane Hutt, the education minister, said she would investigate complaints about inept local authority human resource teams.
TES Cymru has learnt that a vote of no confidence has been passed by National Association of Head Teachers members on Bridgend's HR department.
Iwan Guy, acting director of NAHT Cymru, said heads needed the best professional advice, but it was often sadly lacking. Disputes between heads and their staff over pay or conditions were escalating, but school leaders often felt they had no support, which added to their stress and workload.
Chris Howard, head of Lewis School Pengam in Caerphilly, said there were not enough suitably qualified and experienced personnel in Welsh local authorities, and that they were too stretched.
Gareth Jones, secretary of the ASCL Cymru heads' union, said there was growing concern over the "corporatisation" of HR services.
"Corporate services just don't have a full appreciation of education law," he said.
The quality of the services is inspected regularly by Estyn, the Welsh inspectorate, but not graded.
A survey by the Wales Audit Office and Estyn, covering schools' perceptions of local authority services in 2007, rated Neath Port Talbot's HR service near the bottom.
The survey was undertaken at a time of "extreme tension" between heads and human resources over redundancy fears in the county.
Heads were also concerned that high staff turnover at the authority had led to poor levels of service.
But in its latest report, Estyn said the service had improved and now provided effective support to schools, with each school linked to a nominated personnel officer who had knowledge of education.
But this situation is rare and there is growing dissatisfaction among heads. According to an Estyn report of Cardiff local authority published earlier this week, HR support for schools is good, particularly for staff redeployment and recruitment, but the report said several heads had expressed concern about the consistency of advice provided by different HR officers.
Speaking at NAHT's annual conference earlier this month, Jane Hutt said she was concerned.
A Bridgend council spokesman said it was aware of the union's concerns. "We are continuing to work alongside local schools and are meeting with their representatives to resolve these issues," he said.
Leading article, page 36.