Teaching unions are stepping up pressure on the Assembly government to reduce the pound;500 per-pupil funding gap between Wales and England.
Teachers' union NASUWT Cymru has given the government a deadline of 2012 to address the problem and plans to lobby Assembly members in the run-up to the final budget settlement next month.
NUT Cymru is also planning to lobby AMs at the Senedd on December 8 after gathering thousands of signatures on a petition calling for action to redress the imbalance.
John Tobutt, head of Gabalfa Primary school in Cardiff, proposed the 2012 deadline motion at NASUWT Cymru's annual conference in Swansea last week, which was passed unanimously by delegates.
He said the funding disparity, first revealed by TES Cymru a year ago, was "little short of a national disgrace and an embarrassment that pupils in Wales were being short changed".
Chris Keates, general secretary of the NASUWT, said the funding gap could not be allowed to continue, and that the 2012 deadline was a "pragmatic" goal in the current economic climate. "The need to provide adequate funding for schools cannot be overstated."
Rex Phillips, NASUWT's Wales organiser, said the union would step up pressure on the government to tackle the problem to stave off potential teacher redundancies and staffing cuts.
"The motion recognises the difficulties that would be faced by the government in addressing the situation completely this year but it should be looking to close the gap by 2012," he said.
"The NASUWT will be encouraging members in Wales to turn up the pressure by lobbying their members over this issue."
David Reynolds, professor of education at Plymouth University, revealed the spending gap between Wales and England last November.
Since devolution, the discrepancy has grown steadily, from 1.3 per cent in 1999 to 10 per cent last year. This amounts to several hundred thousand pounds per year for an average 950-pupil secondary school and scores of thousands of pounds for an average-sized primary.
The Assembly government originally dismissed the findings and attacked Professor Reynolds for "running Wales down", but earlier this year its own official figures showed his research was correct.
Further pressure was put on the government in April when Welsh delegates of the NUT used their national conference to attack the way schools in Wales were funded.
Research by consultant John Atkins found that 14 local authorities were spending less on education than they had been allocated, a gap of around pound;66.4 million.
An Assembly government spokeswoman said direct funding comparisons with England are difficult because policy priorities and school funding arrangements have diverged since devolution.
She said substantial funding continues to be made available for learning - including pound;2 billion in the draft budget for 201011.
"Devolution has made it possible for us to take forward a distinctive policy agenda for education in Wales which has been widely welcomed.
"We take decisions on the basis of what we believe is right for Wales, not by reference to developments in England. This will continue to be the case."