The Exclusive Brethren (of Hollow Men fame) want to integrate their private school system to scam more money. Unlike other integrated schools, this will not lead to taxpayers funding religious education - Brethren schools are entirely secular, because they don't trust anyone to properly espouse their beliefs. But as this 2010 article on the schools makes clear, they deliver a substandard education. Brethren schools do not deliver an education aimed at broadening the horizons of their students or encouraging them to achieve to the fullest extent of their capabilities. Hell, they do not even deliver an education in the narrower sense of giving students the baseline skills they need to operate in the modern world. The brethren regard that world - our world - as being inherently corrupt, so they deliberately stunt and cripple the minds of their students so that they will not be able to look beyond the narrow bounds of the Brethren's C19th worldview.
We would not fund a school whose idea of "education" was to crush their students' limbs to prevent them from using them. And we should not fund one which does the same to their minds. If the Brethren want to cripple their children in this way, then they can do it without taxpayer assistance.