About 8,000 children in Brighton and Hove are being forced to miss school because of a 48-hour strike by teaching assistants.
About 60 per cent of the 700 assistants, who are members of the GMB and Unison unions, voted to walkout over plans to cut the number of weeks they are paid.
Out of about 60 primary, infant and special schools in the city, 30 closed completely because of the action.
The row began over proposals by Brighton and Hove City Council to give assistants pay rises, but cut the number of weeks they are paid to work. Unison said most of the assistants are paid for 49.5 weeks a year, or 52 weeks in special schools, but the council plans to cut this number to 44.
The GMB said it did not want schools to have to shut down. A council spokesman said about 90 per cent of assistants would get a pay rise under the proposals.
He urged the unions to accept proposals for the dispute to be referred to arbitration service Acas.