During a speech at the union's 2007 annual conference last weekend, head Robert Howells told of his "grave concerns" over young graduate teachers, many of whom are failing to find posts to become fully qualified.
"Many are on short-term contracts or work through agencies, meaning they are paid lower wages, have no ill-health cover and do not receive pension contributions," said Mr Howells, who is head of Llanybydder primary school, near Llanmyddyfri, Carmarthenshire.
He also hit out at workload pressures on teaching staff, claiming he had been increasingly aware of colleagues taking time off because of stress. He said more heads appeared to be losing health shortly after retirement due to increased pressure at the helm.
Delegates at the annual conference, held in Aberystwyth, hotly debated motions, including one to scrap local authorities.
The motion called for all 22 to be abolished on the back of "fed up"
members who are sick of "the arguments, blame and denial of responsibility"
It proposed that local authorities be done away with and the Assembly become directly responsible for funding education. But the motion was thrown out by most delegates - and rightfully so, according to Gruff Hughes, UCAC's general secretary .
"We certainly need to improve support to schools by the LAs," he said.
"But, as a union, we have always opposed a centrally-based education system."
However, pressure will now be placed on the newly formed government in Wales to take up motions that were carried, including: opposition to the chartered teacher scheme; further review of the education funding formula; support for schools faced with problems due to misuse of modern technology; and proper guidance for schools on statutory changes.