A primary head says he can no longer afford to pay for a nationally recognised nurture group out of his ailing budget.
John Healy, headteacher of Our Lady and St Michael's School in Abergavenny, said the highly rated Rockets group, which was officially launched last month, should be subsidised by his local education authority.
The school's nurture group is the first of its kind in Monmouthshire, and has been praised by behaviour experts.
Children with a variety of behavioural problems are taken out of mainstream classes for several terms and looked after by two teaching assistants during a carefully planned day.
The young pupils, who may be badly behaved, lacking in confidence or unable to concentrate on their work, are then re-integrated into normal classes.
The main objective is to boost the children's confidence and self-esteem during a period when they have been made to feel worthy and cherished.
Since it was established almost a year ago, the unit has looked after 10 pupils and a further 17 are receiving support.
But Mr Healy fears he will have to withdraw funding to meet other financial priorities as his budget plunges further into the red.
"We can only keep this going if we get help from the local authority," he told TES Cymru.
"I think the will is there, and the recognition of the success, but not the finances."
Alison Ward, the teaching assistant who set up Rockets, said: "We have proven that this strategy - early intervention into children's problems - does help. It would be a terrible shame to lose it."
Mr Healy and Mrs Ward want Monmouthshire Council to follow in the footsteps of Swansea, which supports five primary school nurture groups financially.
After last month's launch, the school hosted a conference, attended by Professor Ken Reid, chair of the National Behaviour and Attendance Review. He said the nurture group was the way forward in helping to boost achievement in literacy and numeracy, as well as solving the attendance and behaviour problems in Wales's schools.
"The nurture group has clearly had a positive effect on the school and its pupils," said Professor Reid. "And I think it's extremely important that the school continues this."
Monmouthshire council said it was reassessing its plans for supporting children with social, behavioural and emotional difficulties. A spokeswoman said supporting nurture groups could become part of its new plans.
Nurture groups were introduced in 1969 by Marjorie Boxall, an educational psychologist based in Hackney, east London. They are based on six key principles:
Children's learning is understood developmentally.
The classroom offers a safe base.
Nurture is essential for the development of self-esteem.
Language is a vital means of communication - more than a "tool", it is a vehicle for expressing feelings and emotions.
All behaviour is communication.
Transitions are important in children's lives.