Drink More Water
What's happening to the children?

To the great surprise of parents, kidney stones, once considered a disorder of middle age, are now showing up in children as young as 5 or 6.
...
[P]ediatric urologists and nephrologists across the country say they are seeing a steep rise in young patients. Some hospitals have opened pediatric kidney stone clinics.

Kidney stones are apparently really painful and generally result from a diet of either too much salt or too little fluids, or both. I'm wary of this danger because of calcium deposits in my kidneys that showed up on an x-ray several years ago. Until reading this, I had no idea that I live in the "stone belt" because of the high rate of kidney stones in the South (which has extended to children here as well).

The article makes the case that kids have much more salt in their diet these days, and are reluctant to drink fluids during the day to avoid using the restroom at school.

In general, intake of fluids helps, but the contributing factors in specific beverage consumption are confusing at best. While caffeine intake has been believed to increase risk of stone formation, this study found that in fact coffee and tea both have an inverse relationship to the recurrence of stones (as do beer and especially wine, though all of the other behaviors associated with significant alcohol consumption mitigate any benefit), where apple and grapefruit juice increase the risk. Go figure.