(CNN) - Kids who drink water at school are less likely to be overweight, according to a recent study, but the government says schools are not providing enough to drink.
According to the CDC, the vast majority of young people don't drink adequate amounts of water. Many public schools don't serve water with lunch.
"Water fountains aren't providing the adequate hydration to students," said Matt Sharp, with California Food Policy Advocate.
Lack of hydration is bad for children's health. A study in Germany found making sure kids could drink water at school led to a 31 percent drop in risks for becoming overweight.
A federal law passed in December mandates for the first time that schools, "make available to children free of charge, as nutritionally appropriate, water in the place where meals are served."
The U.S. Department of Agriculture, which is in charge of implementing the rule, said it hasn't decided whether fountains are enough, or if schools will have to find another solution.