Okay, there are a lot of issues here:  generating funds for schools, nationwide obesity, teaching children nutrition, and more...

Here's my own experience with this.  In the school I started my teaching career at, there were vending machines that sold one of the more popular sugar-water "faux juice" drinks (5% juice).  These machines generated a lot of money for the school.  I was not the only teacher to note that many of middle school students who enjoyed those beverages at lunch were "bonkers" with attention problems and other behaviors that made it harder for them to learn in the afternoon.  It was a stark, "Jekyll and Hyde" difference for many of them, too.

Of course, to a sub-par administrator, behavior problems are easily dealt with by assigning a detention, ISS, or some other disciplinary action, but the cash those machines bring in is coveted.  Can this be thought of as exploiting pre-teens for their own good?