"Calories

According to the USDA Dietary Guidelines for Americans, an average teenage girl needs 1,800 to 2,400 calories per day, depending on how active she is. An average teenage boy needs 2,200 to 3,200 calories per day. The higher the level of activity, the more calories required for both girls and boys.


Read more: http://www.livestrong.com/article/274860-how-many-calories-d...

I would say 800 Calories for a lunch isn't that far off (maybe a bit high if inactive, but teenagers tend to be more active than the general population given required gym classes and voluntary sports. But if they are on the more active end, then 800 may not be enough.

Of course, the quality of these Calories provided in a school lunch may no good (mostly from fat and sugars vs carbs).