The UK's only state-funded Sikh secondary school wants to change its admission rules to keep a mixture of faiths among its pupils.
The school is in an area where many Sikhs live
The Guru Nanak Secondary School in Hillingdon, West London, would like to have a 15% quota of non-Sikh places.
It already has non-Sikhs but as it has become more popular, spaces for such pupils are becoming fewer.
Faith schools are not obliged to admit children of other faiths, although some do. There have been calls for quotas.
Critics have argued that faith schools increase segregation in society and one of the reports into the riots in the north of England in 2001 called for all schools to have quotas to ensure communities were mixed.
The Guru Nanak Secondary School's admissions policy gives priority to committed members of the faith, but has in the past admitted pupils of other religions.
At the moment, about a tenth of the 450 pupils are not Sikh, but as the school has become more popular, there have been fewer places for children of other religions.
The school achieved the second best "value added" results to GCSE level in England last year.
Deputy head teacher Greg Hall told the BBC News website: "Our head teacher and our spiritual leader are very keen that more non-Sikhs should be allowed into the school.
"We are interested in reserving a quota of places so that the school remains inclusive."
The school is writing to the local body which oversees admissions and to the Department for Education and Skills for advice.
It opened as a private school in 1993 and transferred to the state sector in 1999.
A spokesperson for the DfES said: "Faith schools can make an important contribution to community cohesion by promoting inclusion and developing partnerships with schools of other faiths and non-faith schools.
"We want to see faith schools working with other schools to bring children of different cultural and ethnic backgrounds together."
The subject of faith schools can be contentious.
Earlier this year the chief inspector of schools in England David Bell expressed concern that some independent faith schools needed to do more to promote principles of mutual tolerance and social inclusion.
The government's approach is to support the creation of faith schools where local people want them.