Children as young as 10 have been making badges and banners in lessons for a TUC-supported protest in east London on November 12 over low-paying companies.
But the children's involvement has angered Conservatives and business groups, who say pupils are being "brainwashed".
The mainly Catholic pupils will join teachers and thousands of other adults on the march, organised by the East London Citizens Organisation.
The idea came from the Citizen Organising Foundation campaign group. Neil Jameson, its chief executive, said the group aimed to "politicise" pupils but without a partisan bias. "Politics is like swimming, you cannot teach it in the classroom," he said. "The only way you learn is by doing it."
The protest will involve around 200 pupils and has been backed by Sir Bernard Crick, who chaired the advisory group which led to citizenship's inclusion in the curriculum. "Citizenship is supposed to be about the difficult issues, and if kids do not feel they are taking part they will be bored," he said.
So far three schools are to join the march: Trinity and Canon Palmer high schools in Redbridge, and St Antony's primary in Forest Gate.
A handful of others is considering bringing pupils to an assembly at which demonstrators hope to meet London Mayor Ken Livingstone.
St Antony's head, Sister Kathleen Colmer, said the march was the climax of a study of wage issues and the East End's history of protest. She was adamant the exercise was not about forcing political views on children. "Our pupils are concerned about doing what is right for the less fortunate," she said.
The idea has been attacked by the Campaign for Real Education and the Institute of Directors. Ruth Lea of the IoD said: "This isn't citizenship, it's brainwashing children at the taxpayers' expense."
The Department for Education and Skills has refused to comment until it has spoken to participating schools.