The immutability of IQ?

Via Yglesias:

Their answer – a provisional one, since they are still refining the research – is that feeding primary school kids less fat, sugar and salt, and more fruit and vegetables, has a surprisingly large effect. Authorised absences, the best available proxy for illness, fell by 15 per cent in Greenwich, relative to schools in similar London boroughs. And relative to other boroughs, the proportion of children reaching Level Four in English rose by four and a half percentage points (more than six per cent), while the proportion of children achieving Level Five in Science rose by six points, or almost 20 per cent.