The thing is nurture can make a massive differences to a DCs life chances.
If parents and schools invest in lower ability DC. Encourage them to do the very best they can they can make huge differences to their life chances.
It matters not on iota if DD1 gets a B or an A* for English GCSE.
It matters hugely if a child gets a C rather than a D.
Supportive parents who could afford to support my DSIS through a secretarial course and a flexible admissions system that let her in changed her life too.