More teaching and lecturing staff are to join the strike that is due to take place next Thursday (30 June).
They are protesting about proposed changes to the Teachers’ Pension Scheme.
The dispute revolves around plans to require public sector workers to make greater pension contributions in return for reduced benefits and a raised retirement age.
Their action will affect dozens of schools in Brighton and Hove, closing some of them.
Longhill, Patcham High, Portslade Community College and Varndean College are among those which have already said that they will be closed next Thursday.
Primary schools closed for the day include Bevendean, Hangleton, Queen’s Park, Somerhill and Woodingdean.
Public servants belonging to the Public and Commercial Services (PCS) union are also striking on the same day.
Members of all four unions will meet at The Level at 10.30am next Thursday and will march to Hove Town Hall for a lunchtime rally which is due to start at noon.