Schoolchildren are doing well to thrive in classrooms that are crumbling because of underinvestment, says Preseli Pembrokeshire AM Paul Davies.
Mr Davies, who is also Shadow Welsh Education Minister, was responding to the news that there is at least a £1.6 billion backlog of school repairs across Wales.
A local education expert estimated this week that schools in Wales are lagging 40 to 50 years behind those in England in terms of physical upkeep.
"This observation was made by the Chief Executive of Denbighshire Council who moved to Wales from England 18 months ago," said Mr Davies.
"He said there was "obvious disparity" between funding for English and Welsh schools and his view was backed up by the Association of School and College Leaders.
"In 2006 a report by PricewaterhouseCoopers estimated there was a £1.6 billion backlog of school repairs and this must be much more now. "If we are to tackle the legacy of underinvestment in school building modernisation the Assembly Government needs to be far more ambitious than it has been to date in accessing all available funds.
"A considerable backlog remains in bringing classrooms up to 21st century standards. Labour and Plaid Cymru's ideological hang up with the private sector is holding back investment and modernisation.
"It is a testimony to the hard work of pupils and dedication of teaching staff that children continue to achieve."
