Maloney said even though her kids will get backpacks through Project Hope donated by Cradles to Crayons, she still has to spend about $100 on a calculator for her 16-year-old, plus $100 or so worth of additional required supplies. "Things will get overlooked because I need money for them," she said.
In many cases, teachers help fill the gap. A survey conducted by the Education Market Association last year found that public school teachers spent, on average, $149 of their own money buying school supplies and another $138 buying things like tissues, wipes and paper towels in the 2012-2013 school year.
Maryia Barone, a teacher at a charter school in the Dallas-Fort Worth area, said her low-income students were most likely to come in without pricier, but critical, items such as binders. "When that happens, teachers wind up paying for that out of their own pocket," said Barone, who estimated she'll spend about $100 of her own money this year.
"It can hurt them socially because they don't have what the other kids have and they know it … and it hurts them in the classroom," Barone said, when kids don't have notebooks to write down their assignments.
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Even with piecemeal efforts by nonprofits and individuals, experts say the bigger picture is troubling. "The quality of your education shouldn't vary with your ability to pay," said Jonathan Zimmerman, a professor of education and history at New York University. "This is a shared responsibility, regardless of the choices that individual parents and families make about their education …. We're losing the public in public education."
Cardinali said expecting lower-income parents to shoulder more of the cost for public school can lead to a two-tier educational experience that shortchanges their kids.
"They lose a sense of belonging. They are, right from the start, set apart," he said. "It materially compromises their ability to learn."
Elizabeth Pitula, who teaches at a charter school in New York City, sees struggling parents spend money they don't have to shield their kids from the effects of poverty on their education. "Poverty hides in a lot of unusual ways," she said. "I have students who are homeless but come in every day in full uniform."
Pitula said she spends about $200 of her own money each year to make sure her students all get the same experience in the classroom. "I tell people I'm a teacher because I believe in democracy, and you can't have a democracy where you educate people differently based on class," she said.
—By Martha C. White, NBC News