Keith Towler, the children's commissioner for Wales, said he was disappointed by per pupil funding inequalities between Wales and England. Responding to Professor Reynolds's research in today's TES Cymru, he said good funding in schools was essential and should be equally available to all.
"It appears this (the research) is another example of an individual's postcode affecting the services that they access and the opportunities that extra funding could afford," he told TES Cymru.
Mr Towler's comments came as a major report says more could be done in schools to reduce child poverty in Wales.
The Assembly's Children and Young People's committee says in its report, which has 27 recommendations, that there needs to be better training for teachers in tackling poverty in Wales and a pilot Welsh scheme trialling free school meals for all pupils should be introduced.
The committee took evidence from teaching unions, charities and Assembly members.
All had expressed concern that school-based schemes to tackle inequality in Wales were underfunded.
Members also heard evidence that parents were having trouble paying for school trips, uniforms and stationery.
According to Assembly government figures, 29 per cent of children in Wales live in poverty.
Nicole James, Wales adviser for the National Confederation of Parent Teacher Associations, said many schools in Wales relied on money raised by parents for essentials such as sports equipment.
"If you look at the school budget the amount that is ring-fenced for school supplies can be very small," she said.