Janet East's son James was due to start at the One In A Million school next week.
He has special needs and she is worried how he will cope in a larger school.
She organised today's protest and hope it persuades the government to change its mind and allow the school to open.
Pupils who were due to start at a free school in Bradford next week should have their uniform costs refunded, says a local councillor.
The Government has pulled the funding for one of its flagship Free Schools in Bradford, just days before it was due to open.