There are “extreme concerns” £9m in funding could be reallocated if a campaign opposing the site for a new Welsh medium primary in Carmarthenshire is successful.
Llanerch Fields in Llanelli is the preferred option for the new Ysgol Dewi Sant.
But some residents have lodged a planning application to designate the fields as a village green.
Headteacher Ann Clwyd Davies said unless the money from the 21st Century Schools building programme is spent on the “carefully chosen” site, it will go to another project, which Carmarthenshire council has confirmed.
Parent and governor Aled Owen described the issues raised by campaigners as “minor”, while councillor Rob James said residents want to “preserve the use of green space”.