You may want to ensure that when your kids head back to school after the summer is over, you're sending them with their own bottles of water.

In a survey conducted by the Government Accountability Office regarding schools testing their drinking water for lead, the results were shocking. In 41% of the districts surveyed, which serves 12 million students, the drinking water had not been tested for lead in a year leading up to the survey.

The survey found that 43% of districts, serving 35 million students, had tested positive for lead with 37% showing some amount of the metal in the drinking water. The remaining 16% of the schools didn't know if they had tested for lead or not.

The GAO states they conducted the survey after elevated levels of lead in school children in Flint, Michigan in 2015 highlighted the dangers of lead exposure, especially for children. There is no federal law mandating testing for lead in school drinking water, and the GAO points out that lead can leach in to school water supplies through the existing plumbing.

"Lead in school drinking water is a concern because it is a daily source of water for over 50 million children enrolled in public schools," the GAO wrote in their report.  “Lead in a child’s body can slow down growth and development, damage hearing and speech, and lead to learning disabilities.”

PREVIOUSLY: How Drinking Water Can Soothe Your Child's Anxiety

"It’s really upsetting that to this day, the lead problem still exists in our country," Olga Naidenko, senior science advisor at the research and advocacy organization, Environmental Working Group, told Romper. "The toxicity of lead has been known for a long time. This is not a new story."

While there is no federal law requiring schools to test for lead in the water at this time, the GAO did note in it's report that many states are beginning to mandate their school districts test for the metal. California, Illinois, Maryland, Minnesota, New Jersey, New York, Virginia, and the District of Columbia all have various requirements for schools to test for lead. Thirteen other states; Arizona, Colorado, Idaho, Indiana, Maine, Massachusetts, Michigan, New Mexico, Ohio, Oregon, Rhode Island, Vermont, and Washington have all participated in voluntary testing.

Many are calling for stricter rules and regulations to keep children safe, hopeful that this new study will be a wake up call.

READ NEXT: Community Rallies Behind Teen Opening Hot Dog Stand To Raise Money For School Clothes