Revised proposals for changes to secondary schools in Bath are due to go before councillors.
Bath and North East Somerset Council earlier announced it was recommending closing Culverhay School.
The authority said there were no plans to make any changes at Broadlands in Keynsham, which had been earmarked for closure.
A consultation had been held into plans to close Culverhay, and either Oldfield or St Mark's and open two new schools.
'Signed and sealed'
The all-boys Culverhay School is around half full and had wanted to introduce girls.
Culverhay head teacher Richard Thomson said: "We're kind of dismayed that the ground seems to have been cut out from under the feet of the school.
"It's not signed and sealed and we're optimistic about the future and we're determined to do the kind of high quality job we do with young people and this community."
In the new plans, the council detailed the recommended merging of St Mark's Church of England School with Saint Gregory's Catholic College.
The all-girls Oldfield school in Bath has applied to become an academy.
A council spokesman said if it did not receive written confirmation that co-educational status had been included in the application, it recommended creating a new co-educational school and proposing Oldfield's closure.
The council said the changes were aimed at improving standards and educational outcomes over the next 20 years. They also responded to the consultation and national education policy, the spokesman said.
The authority's cabinet is due to make a final decision on 21 July.
The spokesman said if the recommendation to close Culverhay was accepted, a consultation would be held.