Parents and children from across Brighton have gathered in the city to protest against plans to change the way schools admit pupils.
A petition signed by 3,000 people was handed to the city council
The council could become the first in the UK to introduce fixed catchment areas for all of its secondary schools.
About 3,000 people signed a petition against it, which was handed over to a councillor outside Brighton Town Hall.
Brighton and Hove City Council said it wanted to make the system fairer and eliminate tactical applications.
But Tracey-Ann Ross, of Schools 4 Communities, said strong communities would be split by the proposals, and traditional links with local secondary schools cut.
Parent Mark Bannister added that the way some of the catchment areas had been drawn would inevitably result in some of the schools being oversubscribed.
He said: "Then the council will use a lottery, or random allocation, to decide which kids get the places, and the method... will result in some kids who live right next to the school gates being sent to schools miles away."
However, the council said it had received a considerable amount of correspondence in support of its plans.
"The proposals give priority to parents applying to their local school or schools... the current system effectively denies this to parents in a number of areas of the city," a statement said.
"No system will satisfy everyone."
The council is expected to finalise its plans at the end of January.