I really don't see the problem here. Look at it from this perspective. My wife teaches at a heavily muliti-cultured, multi-faith primary/junior school in the 'ghetto' (good school to work at despite this), and they include everything they should to keep people of various religions happy. They celebrate Diwali, Eid etc etc, and various other Hindu and Muslim festivals/traditions, so why should Christian assemblies be snuffed out when all the parents have to do is withdraw the kids? It's not rocket science.
Why spend time trying to appease every religion?