Kellianne King was a healthy, vibrant little girl until she started preschool. That's when she started to suffer from headaches, sinus infections, chest pains and seizures, says her mother, Kathy King.
It was a heart-wrenching time for the family. "She would stand on her bed and she would just scream, 'You have to -- you have to help me. Someone has to help me.' And we couldn't do anything," King said.
And Kellianne, now 13, couldn't enjoy many of the pleasures of being a kid.
"I feel like I didn't get to do much," she said. "I mean, I can ride a bike and read a book now but when I was little, I never got to do that. I learned how to do those things much later. So it was hard."
No one, it seemed, could figure out what was making the little girl so sick. "We took her to all the best doctors and they were just perplexed by her," King said. "They really just couldn't pinpoint what was wrong,"
When Kellianne was in the first grade, her parents learned the painful truth: There were serious air quality problems in her school that had sickened dozens of students and teachers.
"I was shocked that the only place, the only place I trusted to leave her was what was making her sick," said King.
Dr. Phillip Landigan chairs the Department of Community and Preventative Medicine at Mt. Sinai School of Medicine in New York. He is one of many doctors alarmed by hidden toxins in schools.
"Today, too many chemicals are put into schools that have never been tested for the possible impacts they have on young children," Landigan said.
Simple leaks can breed deadly mold behind walls and trigger an asthma attack; pesticides used to kill insects and weeds can damage a child's developing nervous system, lowering IQ and affecting attention span.
"Children live down on the floor," Landigan said. "They crawl on the rug. They're constantly putting their little fingers in their mouths. And all of those actions increase the child's exposure."
Just how quickly kids get exposed to toxins in school became clear when "Good Morning America" conducted an experiment in a classroom at P.S. 8 in New York.
First, we applied Glo-Germ, a non-toxic powder only visible under ultra-violet light, in areas where pesticides are most likely to be sprayed or to settle, like baseboards, windowsills and desktops. Then we invited the kids to play. After only 20 minutes, we showed them the stunning results.
Using UV light, we found traces of Glo-Germ all over their clothes, hands and faces.
"It was actually scary to see how germs can spread, toxins can spread all over the place," said teacher Olivia Ellis.
Kids spend nearly 90 percent of their time indoors. Yet there are no specific federal requirements limiting the use of toxins, such as pesticides, in schools, which is why it often takes teamwork to get a school to clean up its act and its air.
Patricia Berkey is the principal of Hastings Elementary School in Massachusetts, where Kellianne attended school and was exposed to toxins. "I think families need to feel comfortable when they send their children off to school that they're sending their children to a safe and healthy environment," Berkey said.
That school took action and, nine years later, Hastings is an award-winning example of a healthy environment school.