P.S. 251 kindergarten teacher Patty Lee helps a student with a math game on an iPad she got through DonorsChoose.org. (Aisha Asif)

When Patty Lee asked her kindergarten students in early October what letter had a “ba” sound, 23 little hands pressed colorful markers hard against the small dry eraser boards on their laps, connecting lines to semicircles. Lee, who teaches at P.S. 251 in Brooklyn, complimented students who showed her the letter “b” while telling others who had written a “d” to try again.

Just a few weeks earlier, this simple exercise would have been very different because Lee, like many teachers across the country, was scrambling to provide the most basic supplies, like markers, for her students. Then she turned to DonorsChoose.org, a crowdsourcing site that allows teachers to request donations for big expenses like field trips and smaller ones like paper. Lee’s colorful markers were among $400 worth of school supplies Lee bought this year — part of a remarkable $105,000 she has received through the site since 2006.

“I’ve gotten really lucky with how much they’ve helped my classroom that I never really thought price-wise how much it was,” she said after a reporter, using information from DonorsChoose, provided her with the tally.

According to the DonorsChoose site, Lee has been able to purchase basics such as paper and markers ($5,612) as well as books that the city doesn’t provide ($14,931). The iPads, LeapFrog Leap-Pads and laptops her students use also came through donations from the website ($10,034). More expensive purchases have included a reading loft where the kids go to cozy up with their books ($10,093). Lee also has used DonorsChoose.org funds to put on student productions of “The Wizard of Oz” ($5,488) and taken her students on trips to Build-A-Bear and pottery workshops ($3,764), among other spending.

According to a 2013 study by the National School Supply and Equipment Association, teachers spent $1.6 billion of their own money on school and instructional supplies in the 2012-2013 school year. Some districts offer teachers limited reimbursements, but even those have been shrinking under budget pressures. In New York City, teachers this year got about $60 each to use on school supplies, down from about $200 several years ago — a figure that teachers said was not close to what they spent each year on supplies even before budget cuts.

The money crunch has led more and more teachers to turn to crowdsourcing websites such as DonorsChoose.org, AdoptAClassroom.org and ClassWish.org.

Teachers need money for books, musical instruments, art supplies and just about everything else in the classroom, says ClassWish.org co-founder Robert Tolmach. “It’s been this way for a while and the budget cuts made it worse,” he said.

The sites use different models but their goal is essentially the same: to help provide teachers with the tools their students need to learn. All three sites do not give cash donations to teachers, but instead direct them to a network of affiliated vendors from which to purchase needed materials using funds that come from donors.

Both DonorsChoose and AdoptAClassroom require educators seeking funds to write proposals that are posted on their profiles on the sites. DonorsChoose, started in 2000 by a Bronx teacher, solicits a 15 percent fee from individual donations to sustain the site, while AdoptAClassroom directs 100 percent of donations to teachers, according to executive director Bob Thacker. Foundations and businesses make up 60 percent of donors to AdoptAClassroom, which was started in 1998 when founder James Rosenberg, a mergers and acquisitions lawyer, mentored at a preschool and was dismayed at the lack of resources available to teachers there.

ClassWish.org takes a different approach. It was designed to act as a go-between for donors looking to fund specific schools — even if the teachers at that school haven’t asked for supplies. Tolmach, who comes from a background in nonprofits, started the site after reading countless news articles about dire needs teachers faced in class. He thought there should be a more efficient way to donate to schools than through typical bake sale fundraisers.

If, for example, someone in Texas wants to help his former elementary school in Miami, ClassWish will reach out to the school on his behalf and the school can then make purchases through the site’s affiliated vendors. Schools can also post their own wish lists or anyone can identify a school not listed on the site and ClassWish acts as the middleman to forward funds.

Recently ClassWish.org launched a “charity mall” that allows visitors to the site to shop on the site for their favorite brands; when they click on a brand’s ad banner accompanying each school or teacher page listed, a percentage of money spent is donated to a teacher’s wish list account, at no cost to the shopper. That donation is funded by an affiliate fee that the merchant pays ClassWish.org, Tolmach said.

A generation ago, parents’ associations were pretty much the only outside source of funding for teachers’ supplies. But these crowdsourcing sites, most of which have been started in the last decade, are becoming an increasingly important resource, especially for schools in low-income communities.

Lee’s school, identified as “high poverty” on DonorsChoose, is in the Flatlands section of Brooklyn. Seventy-nine percent of students get free or reduced price lunch. Even parents who want to help just don’t have the money.

In her first two years as a teacher, before DonorsChoose.org, Lee estimates she spent more than $5,000 of her own money on supplies. But after turning to the site, she has been able to raise far more than she ever could have spent. Chris Pearsall, assistant to the company’s CEO, said Lee never misses an opportunity to propose “imaginative” projects, like the reading loft and production of “The Wizard of Oz.”

Lee’s fundraising prowess is exceptional: DonorsChoose.org says she is one of the nation’s most successful teachers to tap the resources of its website. But she is hardly the only educator to benefit from its model.

According to its website, DonorsChoose.org has helped teachers win more than $200 million to fund over 400,000 projects since 2000. The site also claims that 54 percent of all public schools have at least one teacher who has posted a project on its site. Contributions and grants doubled to over $52 million in 2012 from $24 million three years ago, according to its 990 filing to the Internal Revenue Service.

More than a third of funded projects are for classroom supplies, from paper and pencils to furniture, storage, and recess equipment. Technology and books are the second and third most popular categories, said Pearsall. This year 13,000 projects have been posted on the site, a 33 percent increase from last year, he said, adding that he attributes the growth to improvements in the site’s ease of use and name recognition.

Budget woes in cities such as Chicago and Philadelphia have also pushed teachers to the sites. Both the number of requests and the number of teachers accessing DonorsChoose.org from those two cities has grown by more than 30 percent in the last year, said Pearsall. Bob Thacker, of AdoptAClassroom.org, said requests to his site were up 20 percent nationally (contributions and grants to the site were at nearly $3 million in 2011, according to its 990 I.R.S. forms) but the number from Philadelphia increased fivefold in the last three years.

“The situation now in the Philadelphia school system is horrible,” said South Philadelphia music teacher Chrisostomos Argerakis. “It’s a joke; we don’t even get paper towels in our classroom.”

Argerakis said he spends around $500 of his own money every year to buy basic classroom supplies, but the 43-year-old has had a lot of help in building his music program at the Andrew Jackson School in South Philadelphia, where none existed before he started there six years ago. He managed to get instruments for his students through donations from instrument manufacturing companies, music foundations and DonorsChoose.org. Argerakis estimates that he’s gotten $27,424 worth of supplies and equipment through the website.

Argerakis credits his success to what he called good strategizing that tied ambition to possible funding sources. Now that the school is known for his rock band, he makes sure to advertise his DonorsChoose.org profile on the flyers he distributes at every performance. Funds from audience members have underwritten projects such as getting 18 keyboards for his classroom ($3,200), Argerakis said.

Argerakis rarely goes a month without posting a project. To maximize funding, he also coordinates bake sales and concerts with the site’s dollar-to-dollar program, which matches funding that teachers’ projects get through other donors.

Teachers can’t count on money from these sites and that can be a problem, according to Chicago teacher Deena Heller. She used DonorsChoose.org at her previous school but said she had to wait so long for the responses that she ended up buying supplies herself. Heller, 27, now teaches third grade at a charter school that gives her $500 a year for supplies so she said she no longer has to rely on DonorsChoose.org.

Pearsall said the website has a 75 percent teacher success rate, meaning it is able to get the majority of projects funded on time, and it continues to strive to do so for every teacher.

New York City will reimburse teachers up to $57 this year for classroom supplies through its longstanding Teacher’s Choice program. But Halli Moskowitz, an elementary school teacher from I.S. 171 in Harlem who spent thousands of dollars on school supplies before she started using DonorsChoose.org 11 years ago, called that “a drop in the bucket.”

Moskowitz said she received donations worth $18,000 through the site and enjoys writing proposals, which she says only takes her 10 minutes to do. She finds engaging titles for her projects: “Dice + 32 kids = Oy, the Noise!” raised funds to replace hard dice with foam ones to lower the noise for a project her fifth-grade math students were working on.

But other teachers say the writing process is cumbersome. That’s one reason why Janice Wagman, a biology teacher at Perkiomen Valley High School in Collegeville, Pa., uses ClassWish.org instead. She said she has received $1,000 funding for goggle sanitizers and lab kits through the site.

“I usually spend a lot of time — seriously hours — thinking how to best spend the money or what to spend the money on to make it go as far as possible,” she said.

For those teachers who get the money they need, it’s time well spent. Argerakis, the Philadelphia music teacher, sees about 1,000 students a week in nine grades and oversees two bands. Even with that schedule, he’s been able to write requests that brought in $28,000 over the last six years. “It can be busywork,” he said, “but it’s certainly worth it.”

This story was produced by The Hechinger Report, a nonprofit, nonpartisan education-news outlet based at Teachers College, Columbia University.