I remember reading a book once by George Bernard Shaw, in which he remarked that it's only about one hundred people in the country who are up to the job of being prime minister. The problem, as I see it, is that none of that one hundred now seem to be politicians, even though there is quite a bit of mediocre business leadership, and Oxbridge types, going into politics. It's the privately educated who are on the remuneration committees, and they don't like grammar school boys. Bright kids from comprehensive schools are held back in order to promote most of the other bit dim kids at the comprehensive schools.
All that mixed ability and no streaming theory is a load of bollocks. It can lead to becoming a backward country with an inefficient civil service.
Just being a woman doesn't necessarily make you a good prime minister. I don't think anybody in the Labour party is up to the job either. You need wide and practical experience and not suffer from want of judgment. What the Institute of Fiscal Studies says isn't scientific fact.