More than 1,000 children in south London were sent home from school on Tuesday after teachers went on strike in protest at council plans to create three new academies.
Five schools in Croydon were closed as members of the NUT took part in the one-day action. It is understood that more than 130 teachers were involved.
Dave Harvey, secretary of the Croydon NUT branch, said: "There would not be a single community school in Croydon, only faith schools, trust schools, academies and foundation schools. We describe this as an abdication of municipal responsibility."
Dave Hill, executive director of children, young people and learners at Croydon Council, said: "While we acknowledge the NUT's opposition to the creation of academy schools on principle, there is strong evidence across the country showing that exam results at academies improve at double the national average rate and that they succeed in tackling entrenched low achievement."
Under the proposals, three schools, Ashburton Infants, Ashburton Juniors and Ashburton Community School would become one all-through academy run by the Oasis Trust. Haling Manor School would become another academy for which the Harris Federation is the preferred bidder. Selsdon High could also be turned into an academy. Two other schools could also be turned into trusts.