Yes actually! It's about choice. I think that if there are adequate numbers of people who want to send their children to a catholic school, a protestant school, a muslim school that there should be 'national' schools to cover the demand. It's not about excluding people, if I chose to send my child to a muslim school I wouldn't consider them excluded because they didn't participate in every aspect.
That's why I think ET schools do serve a good purpose. But there should still be choice of a religious ethos in another school if the demand is there.
And yes, I would hope that even schools with their own religious ethos would celebrate aspects of other faiths.