An official consultation by East Dunbartonshire Council found the vast majority of those who responded are against the proposal.
Of 265 responses from statutory consultees, 204 disagreed with the closure of St Joseph's Primary School, in Milngavie, on the outskirts of Glasgow. Of 291 additional responses, 280 disagreed.
The school, which would merge with St Andrew's Primary in Bearsden if the plans go-ahead, is the only Catholic primary in Milngavie.
The Catholic Church said the closure would represent a "serious deterioration" in the provision of denominational education in the area.
Staff and parents at the school are also opposed to the changes, with the extra time it would take to travel to a new school a big concern.
An assessment of the impact on equalities legislation by the council even suggested the proposal could be considered to be indirect discrimination against Catholic families in Milngavie.
Last night, campaigners fighting to keep the school open seized on the findings, calling for the council to scrap the plans.
Laureen McIntyre, chairwoman of St Joseph's, said: "This report highlights the fact parents, pupils, teachers and the Catholic Church all want the council to think again."
Mrs McIntyre said it was "completely unacceptable" for the council to go ahead with a proposal that would discriminate against Catholic families in Milngavie.
"Our children have the same right to be educated in their own community as everyone else," she added.
The council were unavailable for comment.