New figures to be published later will show whether the gap between spending on pupils in Wales and England has grown further.
Last year schools in Wales received on average £527 less per pupil, and unions fear that the divide will widen.
First Minister Carwyn Jones has pledged to make school funding a budget priority.
The assembly government declined to comment ahead of the publication of the statistics.
Some schools near the Wales-England border have already been comparing budgets ahead of the release of the assembly government statistics.
“It’s quite shocking when you see it in black and white”
Gregg Dixon Head teacher, Connah’s Quay High School
Figures show that Connah’s Quay High, Flintshire, is worse off to the tune of £643 per pupil when compared with The Catholic High School, Chester, which is about 10 miles away. Meanwhile, Wrexham’s Ysgol Clwydeog is worse off by £606.
Gregg Dixon, head teacher at Connah’s Quay, described the disparity as “shocking”.
Meanwhile, his counterpart in Chester, John Murray, said if the situation was suddenly reversed, a £643 cut in funding per pupil at his 1,000-pupil school would mean redundancies and bigger class sizes.
‘Really stretched’
“It’s quite shocking when you see it in black and white,” said Mr Dixon.
“Just in terms of level of staffing we are really stretched in everything we do in terms of teaching and support staff.
“With that additional funding we could do so much around that and be able to support learners more effectively.”
Earlier this month it was confirmed that Welsh universities are losing out by almost £80m per year compared to their English counterparts.
On Tuesday the schools inspection body Estyn said standards in nearly a third of schools in Wales were not good enough.
“While I feel every sympathy with my colleagues in Wales, I’d quite like some of the funding they get in Manchester or Liverpool so I could do so much more here”
John Murray Head teacher, The Catholic High School, Chester
Mr Murray said he had every sympathy with his Welsh colleagues, but he claimed the Cheshire education authority was not as well as funded as other English counties.
“Actually, while I feel every sympathy with my colleagues in Wales, I’d quite like some of the funding they get in Manchester or Liverpool so I could do so much more here,” said Mr Murray.
Other statisitics already published show education expenditure in Wales is budgeted to increase by 3.2% in 2010-11.
In Wales, 75% of the total gross schools budgeted expenditure is delegated directly to schools, with local authorities holding the rest centrally.
In England that figure is 90%.
In Wales local authorities have been asked to hold back less, giving more to schools, according to BBC Wales education correspondent Ciaran Jenkins.
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