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School lockers used to be just places for students to store their books and personal belongings. But more and more, those dingy, banged-up rows of metal lockers — along with entire walls and other school property — are being turned into massive billboards, revenue generators designed to help school districts close their budget gaps.

The ads range from local business pitches on school buses to lunch tables adorned with images of Welch's Grape Jelly to wraparound ads that sprawl a full row of lockers and encourage kids to watch Nickelodeon. Some schools even have sold the naming rights to their auditoriums.

School administrators say the advertisements provide the money they need to keep vital programs — or even teachers — in tough economic times. But critics ask whether the money gained is worth the cost: They say schools should not be promoting brand names, and that impressionable children should not be bombarded by advertisements in school.

For decades, schools have allowed businesses to purchase ad space in yearbooks and playbills and to have their names emblazoned on sports scoreboards and team uniforms. But as they increasingly face budget issues, school districts and local legislatures are being forced to weigh the pros and cons of allowing advertising to become prominently displayed on campus.

Minnesota's St. Francis School District on Monday approved wraparound ads on lockers – the first in the state – to gain $230,000 a year for its five schools. A bill before New Jersey's Assembly Education Committee would allow school districts to sell ad space on the sides of school buses, which sponsors say could bring in up to $1,000 per bus. And California's Sweetwater Union High School District is currently accepting advertising proposals after approving a policy to allow advertisements inside the district's 15 high schools — which it expects to generate up to $1 million a year.

"We do budget forums every year, and every year we've had to cut things and parents always said, ‘Why do we have to cut? Why can't we find a way to raise revenue?' One way we could do that was to solicit ads," Sweetwater Union spokeswoman Lillian Leopold told FoxNews.com.

She said the district studied the issue for four months before the board approved a policy through which a vendor, 4 Visual Media Group, would bring in advertisements. Committees then set up guidelines for what kind of advertising would be allowed, and where.

"Each individual principal has met with our purchasing manager to look at where on campus they would be," Leopold said. "They could be in the gymnasium, they could be in the cafeteria, they could be on walls in the common areas at the schools. But they would not be in classrooms … because the classroom is where instruction is happening and we don't want any distractions."

But in some districts, keeping advertising out of the classrooms isn't enough. San Diego Unified School District last week rejected a proposal to allow on-campus advertising, and Oklahoma recently blocked a bill to allow ads on school buses in the state.

The Campaign for a commercial-Free Childhood, a national organization devoted to limiting the impact of commercial culture on children, says students in those districts will reap the benefits of those bans, even though they'll miss out on the extra funds.

"While we are extremely sympathetic to the financial plight that far too many school districts are in, we strongly oppose any advertising in schools or on school grounds," spokesman Josh Golin told FoxNews.com. "Advertising in schools exploits a captive audience of schoolchildren; exposure to marketers' messages should not be compulsory."

Golin says advertisers like 4 Visual Media Group are pushing these plans on schools in an attempt to exploit schools' fiscal crises.

"In a section of its website labeled ‘Elementary School Media Kit,' the company boasts to potential advertisers:

4VMG's unique form of advertising caters to a captive audience where the viewer can't ‘change the channel' or ‘turn the page.'

"The fact that advertising in schools exploits a captive audience is the number one reason (of many) that it's so wrong. But for 4 Visual Media Group, that's the selling point," Golin said.

According to the media kit, the group also offers advertisers the option to display promotional codes on their ads "to allow for promotions such as a coupon to be sent to the viewer's cell phone directly and immediately."

"It's hard to imagine anything more inappropriate than providing advertisers with a platform to send text messages to children while they're in school," Golin said.

Golin says 4 Visual Media Group removed the media kit from its website after Campaign for a Commercial-Free Childhood started writing about its content, but that a copy can be found at the campaign's website.

4 Visual Media Group did not return requests for comment from FoxNews.com.

Lisa Ray, founder of the Minnesota-based group Parents for Ethical Marketing, says the biggest problem with in-school advertising is that it undermines parents' ability to protect their children from commercial messages.

"We can turn the television off and we can keep our kids off the computer if we don't like advertising, but we have to send them to school," Ray told FoxNews.com. "…There really shouldn't be anything in the school that doesn't primarily serve the education of the students, and advertisements serve the needs of the company that's there."

But School Media, a company that specializes in school advertising, says ads can serve the needs of the advertiser and the education of the students. The company is working with St. Francis school district and currently awaiting nine additional pending contracts.

"All of our advertisers are under the understanding that everything has to be nutrition, education or health and wellness based. Anything outside of those parameters won't be allowed within the school," company spokesman Paul Miller told FoxNews.com.

For that reason, Miller said, calling students a "captive audience" isn't always a bad thing.

"They are a captive audience, they're there to learn, they're there to be educated and I think with the messages we're bringing to the school it's just an added benefit for these kids to be aware of what's going on," he said.

Miller said parents in the districts he's met overwhelmingly support the idea.

At least one mother responding to Campaign for a Commercial-Free Childhood's blog on the issue did, too.

Blogger "Jaded Scribe" said that instead of trying to squash children's exposure to advertisements, parents should make sure the ads aren't their only source of information.

"Teach your kids how to be intelligent with shopping, the importance of choosing products with a known good history of quality," she commented. "...Don't want your elementary school student getting 'text-message ads'? Don't give them a freaking cell phone!"

Lynn Setzer, spokeswoman for the Jefferson County school district in Colorado, adds that schools can maintain full control over what kind of ads they'll allow and where. Jefferson County, for example, decided to permit ads on its school buses, but only in an exclusive contract with a local bank, she said.

"They're very tasteful signs and it just says First Bank supports Jeffco Public Schools, so there's really no overt advertising on it," Setzer told FoxNews.com.

Setzer also says the district was very specific about allowing the ads on its buses but not in its schools.

"It's on the outside of the buses so kids are sitting on the inside they're not looking at advertising during their trip. In a school you have kids walking up and down the halls and in classrooms, it's much more of a captive audience," Setzer told FoxNews.com.

But, considering the success of the bus ads, which will generate $500,000 for the school over four years, Setzer says Jefferson County isn't ruling out expanding its advertising boundaries in the future.

"School funding is always going to be an issue for us because of the way schools are funded, and it [advertising] has helped certainly. Anything we can do to generate money would help with the bottom line," she said.

Leopold says, for her district, it seems advertising is the best way to do that right now.

"We're looking at $23 million in cuts this year and over the last four years we've cut $32 million, so altogether that's more than $50 million in cuts," she said. "And if we want to continue providing quality education for our students, we need to find ways of maintaining programs and not cutting them."