Western Civ is based on the Bible. All children from all religions who come to the West better understand that. Korans? Not of Western Civ. Not ok.
You’re both missing the point. By law, if you let Christianity in, you have to let all the other religions, as well as atheism, in as well. The law cannot state which religions are legitimate and cultural, and which are not.
And while you both say that Christianity is legitimate, it’s not even that easy. Would you want your children taught Christianity by Branch Davidians, anti-military Quakers, Lesbian Episcopalians, or any of the other ‘off-brand’ Christian sects?
Even the Bible is not free and clear. The KJV? The Message Bible? Common English Bible? Some Biblical versions are religious and literary abominations.