Eh, metabolism and activity levels matter a great deal case by case, but a general rule of thumb (that's pretty inaccurate usually, but if you want to ballpark) .. 15 x weight in lbs is maintenance calories, 12 x weigh in lbs is 'cutting' calories. Pretty sure that comes from BodyRecomposition.com, and that guy knows his shit if you glance at his articles. My maintenance calories by that level is about 2800, my cutting/ diet down calorie intake would be 2200 as a 185 lb male. Only thing is --- three equivalent meals is pretty odd for the United States. It varies culture to culture, but in the US typically, dinner is the "big meal" of the day, usually over 1000+ calories, if not much more. But yeah ... I guess I can see 850 calories being light for some people. I wonder if that includes beverages. If the vending machines are a free for all soda-wise, then, well, shit. It's probably a bad idea overall. They just need to have non-crap food at the schools --- they need to have decent, satiating health foods--- but I doubt that will be happening in this decade. It just can't be afforded, for one. ---As an aside, what about prison food? I just saw an infographic comparing the foods, and the prison food was deemed slightly better than the school food. I think they both averaged 1400 calories per meal though.
I don't want to get all nit picky because calories are not the main focus of this thread, but that is bullshit. You say yourself that it depends on activity level and metabolism, but then quote a pretty precise formula to find out your caloric needs. There are rough formulas out there for sedentary, lightly active, moderately active, and very active ADULTS' caloric needs (though what you stated is not it), and they even differ for men and women. Everything changes when you're talking about teens or children who are developing.
What part of "rough, inaccurate ballpark estimate" didn't you understand? There is no mathematical formula, no matter how complex, to apply through a computer screen because you would have to measure so many confounding variables, including someone's daily routine which is largely unknown even to that person, that it's better to just start somewhere, test, and adjust based on how your body reacts. Everyone will find the calories they need to maintain, or lose, weight, because the scale will reflect that. Meticulous counting of calories is all that's necessary to discover the input. The scale about once a week --- to discover the output (not daily, too much fluctuation). The scale is a bit harder with a teenager, but if they are becoming orb-shaped it's time to start restricting calories. And a lot of children these days are getting orb-shaped. The best option is to probably stop serving day-old pizza or pseudo-cheese nachos at the cafeteria, but these answers are obvious.
It's been hitting pretty much everything. People love bad parodies, mang. Also, I know some of you like Tim Ferriss and others don't, either way I just saw this on his blog: Nutrition Science Initiative. It's kind of what everyone in the thread has been asking for- nutrition research for the sake of nutrition research, so that the "THIS WAS PAID FOR BY OBAMA" doesn't come up and there's no bias. At least that's the goal, I hope it works out for the sake of... everybody who eats things.