When Lord Moynihan was complaining, a few days ago, the private schools had provided half. May still be so, but it's no surprise. Public Schools have specialist professional coaches in different sports and they have facilities of the top standard; Eton Dorney is the rowing lake of Eton College, for goodness sake; plus they will allow talented pupils to skip lessons for training. And some sports are very much the interest of Public Schools or rich people who send their children to them (rowing, shooting and equestrianism, for example).
The odd thing is that any privately educated child is now a top cyclist. Would have thought that cycling, at least, would be for ordinary people.
State schools will never have what the private schools have because the money and the time cannot be afforded.But if we were like some totalitarian states, which throw money at sport and identify potential athletes from earliest youth, as part of a state programme, we'd certainly do better.