Parents in Houston now have a new tool in their battle against childhood obesity - Cybersoft Primero ParentOnline (warning PDF) allows parents to restrict the choices their children make in the school cafeteria. If you don't want little Billy to have dessert, simply don't allow it in his profile. As well, parents will be able to track their child's choices.
While this indeed may be helpful, it does seem a bit overlordish to me.
At the end of the day, the best way to treat your children is to focus on yourselves. If you take the time to make healthier dietary choices, control your own portions, limit desserts, and make exercise a part of your daily lives, guess what, your children will learn from you. If instead exercise consists of picking up the remote control, food is hurried, dessert is frequent, that's going to be what your children learn.