Between 40 and 50 mums, dads and children demonstrated before a stormy meeting.
Sheffield Council wants to close Wisewood Secondary and Myers Grove School, Stannington, due to falling pupil numbers, and build a new school on the Myers Grove site.
Protesters unfurled banners declaring 'Don't move - improve' and 'Save Our School' outside the meeting at Wisewood School.
Inside, Coun Harry Harpham, cabinet member for children, and Sheffield's most senior education official, Jonathan Crossley Holland, struggled to give a presentation about why they believe the proposals are necessary.
The council says pupil numbers for both secondary schools will drop substantially over the next seven years, meaning each is teaching between 500 and 600 youngsters, compared to about 1,000 at present.
It says the cost of running both schools would be too expensive and, as smaller schools, they would also be vulnerable to financial problems. Instead, it wants to build a new £18 million school on the Myers Grove site, to open in 2011.
Parents repeatedly interrupted the council representatives with loud boos. One shouted: "You want to ruin this community."
Coun Harpham pleaded for calm saying "People have come here to listen on a wet, cold night. This is not a done deal."
Mums and dads showed their support for Wisewood to remain open with an overwhelming show of hands.
Sarah Marsh, whose two daughters, aged five and seven, are due to go to Wisewood, has formed protest group Parents Against Merger with fellow mum Lucy Fairest and set up a petition which so far has 460 signatures. She said: "The council do not want to listen - they have their proposals."
Denise Bassett, of Ben Lane, said: "Over five years, until the proposal goes ahead, are you expecting all the staff at Wisewood who are doing an excellent job, to just sit around and wait and see if they will be in a job?
"Children's education will suffer - state-of-the-art buildings or not."
Jonathan Crossley Holland said Mrs Bassett's fears about teachers was a "fair point" and said the council would look into reassuring staff about their future.
Other parents criticised the lack of public transport between the northern areas of Wisewood's catchment - around Middlewood - and Stannington, which they said would leave them having to catch two buses or face a long walk.
The meeting was one of about 50 which are being held with parents in the Wisewood and Myers Grove catchment areas until January.

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