Budget cuts could undermine the new school curriculum's introduction in 2022, the head of Wales' education watchdog Estyn has warned AMs.
Meilyr Rowlands urged them to be "incredibly vigilant" on head teachers' workload over the next four years.
The curriculum will give schools more flexibility and mean computer programming and IT skills have equal standing with literacy and numeracy.
Ministers said they would "continue to prioritise school funding".
Mr Rowlands, Estyn's chief inspector, told the assembly's education committee care needed to be taken with the workload for head teachers while the curriculum was being rolled out "especially since the culture we're trying to promote is of giving more responsibilities to teachers, to colleges, to head teachers".
Plaid Cymru AM Llyr Huws Gruffydd asked him if he shared the concerns that shrinking schools budgets would intensify those dangers.
Mr Rowlands replied: "Yes, I would. The international evidence shows that how much money goes into an education system doesn't determine how effective it is.
"But, of course, it's true to say if you've got financial cuts, that it creates practical problems for head teachers to make staff redundant and so on.
"It takes a lot of time and effort to deal with cuts."
Mr Rowland's warning came as head teachers spoke of a "quiet crisis" facing schools in Wales due to a lack of funding.
A Welsh Government spokesperson said local councils were responsible for school funding and "not a single Welsh local authority faces a reduction of more than 0.5% in their core funding next year".
"Across Welsh Government we have taken action to prioritise funding to the Local Government Settlement to ensure resources go straight to the front line to support school spending.
"We recognise the strain the UK government's continued austerity agenda is putting on our public services, which is why only last week the education secretary announced an additional £14m to be directed straight to the front line to support every school across Wales."