Parents protesting about the merger of two secondary schools claim it will mean less choice for pupils from different religious backgrounds.
The Inspiration Trust has been given permission to merge Trafalgar College with Great Yarmouth Charter Academy.
Parents fear the latter's Christian values will be imposed on Trafalgar, which opened as a free school in 2016.
The Trust said the two becoming one school in September would benefit all students.
Trafalgar College was founded by the Inspiration Trust on Thamesfield Way in Southtown and it has about 150 pupils.
It is two miles away from the Charter Academy, which is across the river on Salisbury Road.
Trafalgar would close to make a combined academy of 1,500 pupils on an expanded Charter Academy site.
Protestors have previously said their major issue was with the Department for Education "allowing religious change to our school which there is no support for".
Campaigner Louise Alderman, protesting outside Trafalgar College, said the argument that there was not enough demand for two separate schools was spurious.
"We've looked at intake at all primary schools here and in Gorleston and found there were more potential students than places," she said.
The Trust said the combined academy would be a school of "Christian ethos".
The Trust pledged to continue Trafalgar's focus on science, engineering, technology and maths, but current building work on the Trafalgar site would be terminated.
Trust chief executive Dame Rachel de Souza said: "Bringing the schools together was a tough decision, but we believe it offers the best opportunity to secure the broadest, highest quality curriculum for children in the town.
"Now we can get on with working with pupils, parents, and staff to make sure that all our young people can achieve their very best."