As a parent I put a lot of thought into my dc schools. I chose non religious schools for all of them. My dc have visited mosques, cathedrals,churches and can talk to you about aspects of other religions as well.
Given that the final school allocation is done by the local authority and my decisions were based on prospectuses and visits, I would not neccessarily have been aware of the religious ethos creeping in when I chose/was allocated our schools.
I would not be happy to find that my dc was attending a school with religious rules dictating the ethos when I thought it was multi cultural.
I have no issues with religious schools as I believe that they do have a place in our society. I think that if this group of parents want an Islamic school, and perhaps, given whats happened there is a need for it, then an Islamic school could be set up along the lines of free schools?