Schools should be guaranteed a minimum amount of cash per pupil as part of a major funding overhaul, according to a cross-party National Assembly report.
The verdict came after cash-strapped headteachers and governors told Assembly members how pupils had to share textbooks because schools were so hard up.
The immediate introduction of three-year budgets, and an urgent review of how education cash is distributed to local government, has also been recommended.
Heads and unions generally welcomed the Assembly school funding committee's 27 recommendations, intended to give more clarity and accountability to the system. Some have been campaigning for years for an independent review of the so-called "funding fog" surrounding budgets, and of claims that schools in England are better off.
Committee members said they had been "dismayed" by the extent to which education funding is distributed to councils on the basis of how much schools have received in the past - rather than on what they need to cover current and future staffing requirements, accommodation and equipment.
They also supported comparisons with funding levels in England, while recognising these should not drive policy in Wales. But they denied there was a postcode lottery, claiming local authorities had been "hamstrung" by a system based on historic patterns.
Professor David Reynolds, a leading academic who gave evidence to the committee, said: "These recommendations go into unchartered territory - the traditional independence of local government, which has always been sacrosanct in Wales."
But councillor John Davies, the Welsh Local Government Association's spokesperson for lifelong learning, said: "The report is an interesting contribution to the Welsh education debate. The Association will scrutinise its 27 recommendations."
However, there was some scepticism. Chris Howard, head of Lewis boys school in Pengam, Caerphilly, and spokesman for the National Association of Head Teachers Cymru, said: "Will the Assembly government do anything tangible in the short term?"
But Association of School and College Leaders spokesman Brian Lightman, head of St Cyres, Penarth, said: "This report sets out to help school leaders to deliver the Assembly government's ambitious agenda for reform, as specified in the Learning Country 2 and the 14-19 action plan."
Committee member Janet Ryder, Plaid Cymru's shadow education minister, said: "The report carries a clear message for the government - that despite all the minister's protestations that Labour is funding schools adequately, it blatantly is not."
Jane Davidson, minister for education, lifelong learning and skills, refused to comment, pending a debate next month. In her evidence, she supported the present funding formula.
The committee was set up after the minority Labour government was defeated in a Plaid Cymru-led debate last year. William Graham, Conservative chair of the committee, said many "complicated" issues were still unclear.