Local authorities which apply 1 per cent efficiency cuts to school budgets will face teacher redundancies and put added pressure on heads already "struggling to make ends meet", according to the new president-elect of the National Association of Head Teachers (NAHT) Cymru.
Gareth Jones, head of Ysgol Derwen primary school in Flintshire, warned local authorities not to make their cuts by targeting schools, and called on the Assembly government for clearer guidance to spare schools additional pressure.
The government says cuts in school budgets do not of themselves represent efficiency gains. These should come from better management of staff time and public buildings, for example.
But Mr Jones said: "There is currently no clear guidance to local authorities on where to make their 1 per cent cut and some are applying it to school budgets.
"At a time when budgets are already tight, another 1 per cent could lead to redundancies in schools where there is no need to downsize, and put the 30-pupil class size limit under threat."
Mr Jones, who was due to make his first speech as president to today's NAHT Cymru conference in Ewloe, north Wales, will tell delegates that any cuts will put more pressure on heads already buckling under the impact of the workload agreement.
While the requirement to have planning, preparation and assessment time (PPA) has been good for teachers, heads say they are being forced to take on more teaching themselves because they cannot afford supply cover.
"I have serious concerns about the workload of heads," said Mr Jones, who has been a head himself at Ysgol Derwen for 20 years.
"PPA has had a negative impact on heads. They are covering for teachers by teaching themselves because their resources will only cover the cost of a teaching assistant. Some of the schools who have gone down the route of employing teachers to cover for PPA have found themselves in financial difficulty. This will be happening more often."
Mr Jones is also concerned about the allocation of funding. With variations of up to pound;1,000 per pupil depending on where they live in Wales, he wants the government to make allocations fairer.
"At the moment, local authorities decide the priority for funding, but education may not be the priority in some areas," he said.
"We would like the Assembly government to do something rapidly to address the low funding in some parts of the country. We have also been concerned for some time that many schools do not know how money is allocated.
"There needs to be more transparency in how local authorities allocate resources and for heads to be involved in the process," (see story right).
Financial pressures and the increasing workload are making headships far less inviting as a career and are putting off prospective candidates, according to Mr Jones, who believes Wales needs a National College of School Leadership like England's. But NAHT Cymru is concerned that the Assembly government does not share its fears about recruitment.
"The role of the head needs to be more appreciated and given the due credit," said Mr Jones.
An Assembly government spokesperson said it had established a robust programme of support for aspiring, new and experienced school leaders, who can also access NCSL courses.