I want to see him doing something similar to what he did in the UK version of this a few years ago, where he gathered some of the children around a worktop and showed them exactly what went in chicken nuggets with all the preservatives and reformed meat. Maybe do that presentation in front of some of those hard faced lunchladies... sorry, "cooks", just to really pound it into them. Just like he did with the woman at home, the first step was shock tactics and the sudden realisation of what's really going on clearly hit that woman like a brick.
They probably need it, particularly since when he asked them if they knew what all the ingredients were the head lunchlady just bluntly said "Well, I know Chicken, that's the first one!" yet was obviously clueless about the other 57 ingredients on the box.
Also I'm quite appauled at the headteacher suggesting that this was "all just TV". If Jamie maybe took this show to a fast-food restaurant and said "let's scrap the cheeseburgers and start putting out salaRAB only" then maybe that could be seen as a piss-take, but for him to try to change the habits of a school cafeteria and be shot down by the principal saying it's "all for TV", well quite frankly I don't think any self respecting person would take TV cameras into a school kitchen and radically change the menu, exploiting primary school children for the purposes of entertainment. To be honest, I'm disgusted the "principal" would even have that thought.
And in all honesty, if I were Jamie, I'd just give them all a copy of "School Dinners" from a couple of years ago and tell them to watch it a few times until the message sunk in.