A legal challenge over plans for two new Catholic schools in the London Borough of Richmond is being heard at the High Court.
The British Humanist Association and another group claim Richmond Council broke laws in approving new schools which can prioritise Catholic children.
The schools, one secondary and one primary, are due to open in September.
The council says a democratic decision was taken to approve the schools.
It says it is confident it acted lawfully in approving plans for the schools put forward by the Diocese of Westminster. Families have already applied for places at the schools.
In August, the High Court gave permission for a judicial review of the case, which is now being heard.