Headteachers in Conwy county have signed a letter condemning proposed cuts to school budgets.
Conwy council has indicated that funding could be cut by 6-10%, although the exact number has not been decided.
Headteachers warned the most vulnerable children needing extra support would suffer the most.
The council said it had "no choice" but to reduce its spending, "just like other authorities across the UK".
The council faces a financial black hole of £25m and is likely to cut services across the board.
It could also raise council tax by as much as 11%.
Every headteacher in Conwy county has signed a letter condemning the proposed school budget cuts.
The letter is being sent to parents of children attending primary, secondary, and special schools across the county.
"It is fair to say that any cut being proposed on schools is going to make setting a balanced budget an extremely challenging situation for headteachers and governing bodies," the letter reads.
"The financial situation in schools is now critical and there can be no doubt that further cuts to school budgets will have a significant impact on what we can provide for our pupils.
