Finance minister Jane Hutt has defended the Labour-Lib Dem deal on the Welsh government's £14.5bn budget after other parties demanded a bigger focus on the economy and the NHS.
The agreement promises more money for the poorest school children with £20m saved from this year's spending.
Ms Hutt said it showed "careful financial management".
Plaid Cymru said the "cheap deal" was "bad news". Conservatives said the Lib Dems backed Labour's "savage" NHS cuts.
The last-minute deal announced on Friday followed weeks of talks.
The Welsh government had until Tuesday to table a final budget before a crucial vote on 6 December after all three opposition parties rejected Labour's draft version.
With 30 of the Senedd's 60 seats, Labour needed at least one opposition AM to ratify its budget.
Plaid Cymru had been seeking "a substantial package of measures for jobs and businesses", with the Conservatives wanting a boost to the health department.
Under the budget deal, Labour has also agreed to consult the Lib Dems on the spending of any additional funds Wales could receive following the chancellor's autumn statement on Tuesday.
Ms Hutt told Radio Wales the extra pupil funding was in line with Labour's policy programme, despite claims from Plaid and the Tories that ministers had already rejected the idea.
"We want to ensure that we improve the chances of young people, particularly children in the most disadvantaged areas of Wales," she said.
"This is on top of money that we already allocate to children eligible for free school meals.
"We must recognise that this is a direct link to tackling child poverty, to improve their chances which will have a direct impact on their life chances and their skills for the future."
The funding was money the Welsh government was carrying forward to next year with the agreement of the UK government, she said.
The extra money boosts the size of the pupil deprivation grant to more than £32m next year.
Officials said £450 would go directly to schools for every child receiving free school meals.
There were 70,800 children entitled to free school meals in Wales last year.
Plaid Cymru education spokesman Simon Thomas said: "We really wanted extra resources above and beyond this rather pathetic £20m to go to directly to supporting the economy in Wales.
"They've had six months to put together a budget that reflected the fact that we weren't coming out of recession in Wales.
"The key question is what will the economy be like next year under this budget? The government has signally failed to recognise the difficulties we're in."
Tory opposition leader Andrew RT Davies said: "What is regrettably clear is the Liberal Democrats' endorsement of Labour's savage cuts to the NHS.
"We already know this budget will rip hundreds of millions of pounds out of our health service, at a time when waiting time targets are already being missed, vacancies are not being filled and front line staff are being cut."
However, a teaching union has welcomed extra funding for the least well-off pupils.
ATL Cymru director Philip Dixon said: "The extra money will help schools boost the support they are giving to youngsters from deprived backgrounds, and go some way to closing the notorious funding gap in per pupil spend between Wales and England.
"Our children are our future and investment in them is investment for all. Both Labour and the Lib Dems deserve credit for ensuring that our children, especially those in most need, will now get a better start in life."
Liberal Democrat AM Peter Black, who helped broker the deal with Labour, said: "The pupil premium will begin to break the link, school by school, community by community, between poverty and attainment that has dogged our education system for so long."