It doesn't engage with the argument. And let's say he doesn't in certain circumstances - that doesn't mean that there he is necessarily being a hypocrite as it is perfectly possible to have general principles that can be in conflict with each other - for example 'it is wrong to lie' and 'it is wrong to cause harm'. I could and indeed do hold them as general rules but if a Nazi asks me if I know where the Frank family are, and I know they are upstairs in the attic, then me say 'Not a clue' doesn't to my mind make me a hypocrite, and it doesn't mean to say that any argument for lying being wrong is incorrect.
But I'm sorry Sane we need to know what his argument is.
Is it religious schools stop children mixing full stop or what?
What is his focus. Is it religion or is it Mixing?
He needs to clarify and provide context.
Why did he not just say segregated schools prevent children mixing? We need to get his perspective on what it is he is actually saying.