The Liberal Democrats claim Wales would gain an extra £560m a year due to their election pledges on education.
The party has unveiled a £10bn boost to schools in England in its manifesto.
Education is devolved, so more spending in England triggers extra cash for the Welsh Government to use as it sees fit.
Pledging to stop Brexit if it wins a majority, the party says it would herald a wider remit for the assembly with powers over policing and prisons.
Lib Dem plans to spend more on services in England would generate an extra £1.87bn for the Welsh Government in 2024/25, they said.
That compares to the Welsh Government's revenue budget of around £14.4bn this year.
"The election of a Liberal Democrat majority government on a clear stop Brexit platform will provide a democratic mandate to stop this mess, revoke Article 50 and stay in the EU," the manifesto, launched Wednesday, said.
"We are unashamedly fighting to stay in the European Union, and we are the strongest party of Remain."
Welsh Lib Dem leader Jane Dodds said she would urge ministers in Cardiff to spend the extra money promised on schools, to give children "the best start in life".
Her party colleague Kirsty Williams is education minister in the Labour-led Welsh Government.
"Our ambitious plans to reverse cuts to education in England would provide £560m more that the Welsh Government can spend on our schools and teachers, to ensure we continue to build an education system fit for the 21st Century," Ms Dodds said.
The Lib Dems say the money would come from what they claim would be a £50bn boost to public finances by cancelling Brexit.
Analysis by Daniel Davies, BBC Wales political correspondent
Funding for public services in Wales would be 13% higher in five years compared to this year's budget, under the Liberal Democrats' plans.
Inflation will eat into that, and we cannot yet compare it to detailed plans from Labour and the Conservatives who have not published their manifestos.
The biggest contribution to the Lib Dems' extra spending is based on the economic growth they expect to see if Brexit was cancelled.
Although forecasts say the economy will grow faster if the UK were to remain in the EU, that cannot be guaranteed.
The Lib Dems also intend to raise money by putting 1p on all income tax bands.
The Welsh Government is free to spend its budget - including any additional funding - on its own priorities.
It also has powers to vary the level of income tax so could remove the 1p tax rise if it wanted.
Revenue funding covers day-to-day spending, such as wages, and does not include the capital funding that pays to build infrastructure.
What are the Lib Dems' other policies?
The manifesto pledges a "written, federal constitution" that would make the National Assembly for Wales and the Scottish Parliaments permanent institutions.
As it stands, the assembly can technically be abolished through an act of parliament.
The Lib Dems would devolve powers over criminal justice to politicians in Cardiff Bay, giving them control over youth justice, probation services, prisons and policing.
Criminal justice in Wales is currently overseen by the UK government in London.
Plans for policing promise to invest £1bn across England and Wales to restore community policing, "enough for two new police officers in every ward".
The Lib Dems promised to separate England and Wales' legal systems to reflect the growing difference in laws, and to devolve air passenger duty.
Police and crime commissioners would be abolished and replaced with local boards made up of councillors, while the party would fund a two percent pay rise for police officers.
The Lib Dems said it would include the Welsh Government on UK policy making on drug policy and student visas, and create a joint climate council of the nations to coordinate action on the climate emergency.
On funding for Wales, the Lib Dems said it recognised that Wales is underfunded and will seek "over a parliament to increase the Welsh block grant to an equitable level."
Wales' devolved services are mostly funded from the block grant, which comes from the UK government.
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