The NSW government has buckled and signed on to the federal government's $1.2 billion computers-for-schools plan after allegedly demanding an extra $245 million to cover implementation costs.

The move comes hours before the deadline for states to register for the plan -- a key election promise -- which will deliver laptops to every school student between Years 9 to 12 by 2012.

In leaked media reports yesterday, it was alleged NSW Treasurer Michael Costa had demanded the federal government foot the bill for implementation of its computers received under the plan.

NSW has received $56 million out of the $116 million available in the first round of funding which would supply 116,820 computers to 896 schools at a ratio of about two students per machine.

The plan may be a rotten apple for the states who must pay maintenance and support costs which will total up to four times the cost of deploying the computers, according to figures held by the NSW Department of Education and Training.

The pre-budget figures state that $3 to $4 must be spent on maintenance and support for every $1 allocated to the purchase or upgrading of computers.

South Australia and Western Australia have also expressed doubt over whether the $1.2 billion is sufficient to supply laptops to the country's 1 million school children.

NSW Teachers Federation deputy president Bob Lipscombe said the government placed its emphasis on deploying computers and ignored implementation costs.

"If the federal government does not allocate sufficient funds to meet these costs, it is clear that the state government will not pick up the shortfall," Lipscombe said.

"The rollout of computer technology into NSW public schools has for too long been characterised by poor decisions; a lack of regard for the views of the profession and an emphasis on providing hardware to schools with little regard for the professional development, infrastructure and technological support necessary to effectively utilise it."

The states could be forced to fork out an extra $3 billion, WA premier Alan Carpenter told the 7.30 report..

Prime Minister Kevin Rudd told media outside a community cabinet meeting in Mackay that the funding shortfall will be addressed at a Council Of Australia governments (COAG) meeting on Thursday.

"We will continue to negotiate [with the states] but the program will go on," Rudd said.