Jamie Oliver won't change much on his own, but good on him for trying.
He did the same thing here in the UK. I was personally shocked to see the **** that gets served as "food" in state schools in the UK. It's borderline criminal to a) for the state to be feeding this to kids on a daily basis b) create a normalised behaviour of eating junk food daily c) counter-productive because it ends up costing the state a lot more on the long-term due to all the health problems.
I went to a french state school, and the food we were served was quite disgusting but extremely healthy. If that's the food you get during the day at school, and in the evening with your parents, it informs your future eating habits. They don't teach Home Ecs in french state schools, they don't teach nutrition, nor anything like that, but you're surrounded by a culture of cooking fresh food. I have a balcony in London, not even a garden, and I grow tomatoes, chilli, olives, basil, dill, and a few others when the weather permits.
And I still go to McD's like once a month.