Campaigners have warned that the potential closure of a primary in Ayrshire could "open the floodgates" for other rural schools to be shut.
East Ayrshire Council has approved in principle the closure of Crossroads Primary near Kilmarnock, which has 52 pupils.
The council said the building was inadequate and too costly to replace.
The Rural Schools Network said the closure "flew in the face" of laws created to protect smaller schools.
It pointed to the fact that it was the SNP who proposed the new legislation to safeguard rural schools after making it one of their manifesto commitments.
Sandy Longmuir, spokesman for the campaign group, said: "Yesterday was a very black day.
"SNP-led East Ayrshire Council voted to close a 52 pupil school. We think this will open the floodgates now."
He added: "If the SNP can close a school of that size, with the good educational record it has and the parental commitment involved in trying to assist the school, then what chance do the 500 and odd schools that are smaller than that in Scotland have of survival."
East Ayrshire Council has insisted a final decision on the future of Crossroads Primary has not yet been made.
The closure proposal is due to go before the local authority's governance and scrutiny committee on Friday and will then be looked at again by the council's cabinet next week.
Campaigners have urged the Education Secretary Mike Russell to use his power to call-in the decision made by the local authority and ask it to reconsider or reverse it, if the closure option is granted final approval.
Mr Longmuir added: "It is fairly critical that Mr Russell does call this case in and look at it.
"This is the benchmark. We know that councils across Scotland are looking at what happens here.
"It is a test case for the new legislation."