It's a staggering statistic: Hundreds of thousands of schoolchildren in New Jersey are lacking the appropriate afterschool supervision, according to a new survey by the Afterschool Alliance.

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While the survey estimates that more than 260,000 Garden State kids are without adult supervision in the afternoons, the real number could be much higher than that.

"We definitely have some afterschool deserts in New Jersey; the problem is, it's never been formally mapped because in the Garden State, we have what are called exempt programs," said Diane Genco, executive director of the New Jersey School-Age Care Coalition, the statewide network for afterschool communities. "That means that if a public school runs an afterschool program, there is no record of it existing unless we've identified it somehow. In many cases, we have no idea where these programs are, who they're serving, or if they're available to people."

The 2014 edition of "America After 3PM" found that demand for afterschool programs far exceeds supply, and the number of children who would participate in such programs if they were available surpasses the number of children who are actually enrolled in them. The survey included 30,000 households nationwide and 320 interviews in New Jersey. It found that 16 percent of New Jersey students, or 231,279 children, are enrolled in afterschool programs. That is up from 14 percent in 2009. But the large number of unsupervised children remains.

"Because there is no tracking and there is no monitoring of so many of these programs, I can't even begin to say how many children are in need of afterschool care," Genco said. "We have no idea how many kids are out there. No one has ever done the math because we can't access the public school-run programs. It's this big, vague unknown, unfortunately."

Genco is in support of a bill sponsored by Assemblywoman Mila Jasey that would establish an Out-of-School Time Advisory Commission. The commission would bring different departments together with school officials to problem-solve, and come up with a strategy to see if a mapping project could be done -- and to come up with hard, concrete numbers to see where the most needs are.