A second-year pre-kindergarten teacher at Salem Elementary School in Apex, N.C., Hannah Martin makes about $34,000 a year and in her spare time takes as many babysitting jobs as she can get.
Martin, who rents a room in a house she shares with four other women, said the work outside her classroom is necessary if her students are to have the school supplies they need.
"I only have $100 from the school for the whole year to buy supplies, and it's not enough," 23-year-old Martin said.
"I do the babysitting to help get money to buy toys and books," she said. "I even had to buy shelves and a stool for the kids to stand on to wash their hands at the sink. I spent about $500 on supplies last year, and It definitely hurts my own pocketbook."
With school budgets across the country slashed, Martin is part of a growing number of teachers spending more of their own money for school supplies, according to a recent survey from insurance firm Horace Mann, which focuses on products for educators.
(Read more: Six college courses that help grads land jobs)
The problem has reached near-crisis levels, especially in states like North Carolina.
"We're letting our teachers know how rough the situation is," said Eric Moore, a fiscal accountant at the North Carolina Department of Public Instruction. "We've only got about 35 percent of our past budgets for supplies this year.
"After the Great Recession, decisions were made to cut supply funding instead of teaching positions, and we're still facing that lack of funding," he said.
According to the Horace Mann survey, 53 percent of respondents said their budgets for classroom supplies have been cut. General items, including paper and pens, top the list of materials not covered sufficiently by current budgets, followed by math and science tools, then reading material.
The survey said that 26 percent of the 814 teachers participating spent $400 of their own money on supplies last year—that's a 3 percentage point increase from 2011 in the number of teachers spending that much.
"It has gotten worse for us ... especially since we haven't received a raise in seven years," said Mallori Lucas, a reading and language arts teacher at Union Township Middle School in Valparaiso, Ind.
"I was out about $500 last year and $600 the previous year buying supplies," said Lucas, who has been teaching for 21 years and has a base salary of $55,000 a year.
(Read more: Why more parents are choosing 'one and done')
"Of course we're not forced to spend our money. But some of these kids don't even get breakfast before they come to school, so we buy them snacks and treats," said the single mother of two teenagers.
Increasing numbers of teachers also are going online to seek financial donations for items including pens, paper or computers. Others seek supplies for specific projects, such as field trips or science fairs.
"We've had a 30 percent year growth from last year in the number of requests from teachers," said Charles Best, CEO of DonorsChoose.org, an online nonprofit charity group that matches donors and teachers for supplies and projects.
Horace Mann is among the contributors to teacher projects on DonorsChoose.org.
Let our news meet your inbox. The news and stories that matters, delivered weekday mornings.
"It's clear that the reason for the increase is that so many teachers have to use their own money these days," Best said. "That's especially true in the lower-income school districts."
A California-based group that offers cut-rate prices on school materials said it has never been busier.
"We just completed our back-to-school sales, and we had thousands more teachers coming in than ever before," said Greg Brown, senior director of RAFT (Resource Area for Teaching). "They're stocking up on supplies they can't get from their schools. Teachers are forced to pick up the slack."
Spending their own money on supplies is almost part of teachers' job description, said Arlee Hall, a 42-year-old kindergarten teacher at Donald E. Suburu Elementary in Bakersfield, Calif.
"In my second year of teaching, I spent $2,000 on supplies, from books to pens to fruits for the classroom," said Hall, who is married and the father of two adult children. "I also bought shoes and jackets for some of the kids. My family and I missed out on some vacations, but I'd spend the money again."
"I'm not spending as much now," said Hall, who started teaching in 2000 at a salary of $35,000 and now makes around $50,000 a year. "But it's still tough when it comes to supplies, as our class size is growing. They give us one ream of paper a week, and that's it for all the work that needs to be done."
With only 9 percent of total K-12 education funds coming from the federal government, most money for schools comes from state and local funding.
But continued cuts—and low spending even at prior levels—are forcing officials to be creative, said Moore at the North Carolina Department of Public Instruction.
"What we're trying to do now is to pool supply resources among school districts as best we can," Moore said. "It's a top issue for us to try and make sure the kids get the supplies they need."
California students may be a bit luckier. In an email to CNBC.com, the state's superintendent of public instruction, Tom Torlakson, said, "I appreciate the great sacrifices teachers make by taking money out of their own pockets for supplies for their students, especially after years of budget cuts that will soon be alleviated by the governor's budget and passage of Prop 30."
Proposition 30 was the state tax increase passed by California voters last November. In June, the Democratic-controlled Legislature passed Gov. Jerry Brown's budget calling for a $38 billion increase in education spending for grades K through 12.
But unlike California, many states, including Florida, Texas and North Dakota, are keeping education cuts. And voters don't seem likely to pass school budgets that call for higher taxes when they're voting for cuts.
"We had a referendum last year on about $1 million for the budget," said Lucas at Union Township Middle School. "It's good it passed and taxpayers aren't happy. But there's still come cuts happening."
"Everyone's trying to make ends meet, so it's understandable that parents don't want to see their taxes raised, even if it means more money for school budgets," Hall, the kindergarten teacher, said. "They're stuck in the middle. The kids and parents end up suffering."
A full effort is needed to get anything done, said Moore of the North Carolina Department of Instruction.
"We're trying to encourage outreach to the legislators about this," he said. "If we are to get more money from the state, it will have to come from parents, teachers and everyone pushing for it."
While expressing hope that the situation may improve, some envision only darker days ahead.
"I don't see how this gets any better," said Lucas at Union Township Middle School. "Cuts keep happening. It's too bad, because this is such a great school."
"I see how this affects my kids," said Hall at Donald E. Suburu Elementary. "They don't always have the tools to learn. It's always been a problem, but it's much worse now. California's budget should help us, but other states won't benefit from that."
(Read more: $ave me: Making the grade for back-to-school purchases)
Martin at Salem Elementary said she isn't digging as deeply into her own pocket this year.
"I bought a lot last year, but items like Velcro and magnets that will last longer," she said. "I keep receipts, but I'm afraid to look at what I've spent.
"We're all doing the best we can, and we're not complaining. We just want the best for our kids," Martin said. "There are other things I could do with my life, but I love teaching. It's in my blood, so I'll continue to do what I can for the kids."
—By CNBC's Mark Koba. Follow him on Twitter@MarkKobaCNBC
More business news:
Follow NBCNews.com business on Twitter and Facebook