From your article:
"Carmona said she initiated the policy in 2005 after observing students bringing “bottles of soda and bags of flaming hot chips” for lunches on field trips. "
The elementary school many have cited is Little Village Academy, the one I mentioned.
And this regarding the preschool thing:
"However, the administrator’s apparent decision does not necessarily reflect federal or state policy, given the power of individual administrators to make such decisions."
I don't agree with any ban on parents being allowed to send any reasonable lunches to school with their children, including for allergy reasons (I like better the idea of having separate tables that are allergen free tables). But the reality is that the federal guidelines on nutrition are not what is responsible for any of these bans, the individual schools and school systems are.