Wearing smart red shirts and crisp khakis, they stand out amid the hundreds of people flowing through the dusty port of entry here each day into the United States.
From kindergartners to 12th-graders, these children routinely cross the US-Mexico border to attend Arizona schools. Some use fake documents. Others stay with US relatives. All pose as full-time US residents to obtain a better education than they would receive from Mexico's public schools.
Now, however, a growing number of school districts in the Southwest are cracking down on the presence of illegal immigrants in their classrooms as education budgets tighten.
The moves are touching off a deeper moral debate that underlies almost every issue dealing with illegal immigration: Is it better to help the immigrant children and thus improve their lives, or is their presence behind American desks robbing taxpayers - and schools - of much-needed money?
In a time of shrinking funds for everything from band to baseball, many cities are deciding they don't have the luxury of playing tutor to the world. For instance, Nogales is spending up to $125,000 a year to keep illegals out of their schools - including sending "monitors" to the border to catch Mexican children as they come across. And in Chula Vista, Calif., a rapidly growing town south of San Diego, schools officials now require parents to provide proof of residency every year.
"I don't intend to be the US Immigration and Naturalization Service," says Kelt Cooper, the superintendent of the Nogales Unified School District. "But I don't think it's our moral obligation to educate students who don't live in my district."
No one knows for sure how many illegal children are being educated in the US each year - or even whether that number is growing - since no state or federal agency is tracking the phenomenon. Under federal law, school districts are not allowed to ask parents or children their legal status when they enroll children in school. But state law requires proof that students live in the district.
Experts believe that the number of illegal students is substantial. Here in Nogales, for instance, a recent crackdown netted almost 200 children attending local schools under false pretenses. At the border, children have answers ready when questioned by a reporter if they attend school illegally.
"The kids I know from school, they all live on the Arizona side," says one boy, a seventh-grader, as his mother scans colorful windbreakers in a store window. Another boy, a gregarious and slightly chubby 11-year-old, says he goes back and forth every day "just to visit my abuela (grandmother) who lives in Mexico. My best friend goes with me, because his grandmother lives there, too."
They might be telling the truth. But proving that creates big burdens for fiscally strapped schools. Mr. Cooper estimates that up to 10 percent of his district's approximately 6,000 students may still live in Mexico. Each costs the district about $5,000 per year to educate, in what he calls "a fraud on the government and the taxpayers."
Now the Nogales school district is spending precious funds to stop the practice. Administrators regularly search their databases for suspect student addresses, such as one home that was listed by 30 students. And Cooper regularly sends monitors to the ports of entry to check on students coming across. "They're easy to spot," he says. "They're usually wearing uniforms - red shirts and khaki pants.
To get a clearer picture of how many children cross the border, Arizona superintendent of public instruction Tom Horne has asked the state attorney general to investigate the scope of the problem. He says taxpayers deserve nothing less, especially since "state budgets are tight all over right now. People naturally feel uneasy if they feel their government is tolerating a scam without looking behind the surface."
It's a sentiment shared along the border. In Chula Vista, parents increasingly complain that children from Tijuana add to crowded classrooms. In response, Chula Vista officials now require parents to provide proof of residency each year. While anger simmers, however, many Chula Vista residents are afraid to speak out, fearing they'll be labeled as racist. But when the San Diego Union Tribune highlighted the district in a recent story, the newspaper received a flood of e-mail supporting the crackdown.
Those who study border relations caution that solutions should consider the complexity of the issue. "It's one of those situations where legal questions become moral questions," says Gabriela Lemus, policy director for the League of United Latin American Citizens in Washington, D.C. "My sympathy is always with educating children. But we need to find an open way to deal with it, because there is a cost to both taxpayers and communities."
Not all border community members want to keep Mexican children out. From her perch behind the counter at Andres Tienda general store in Nogales, Mercy Johansen watches youngsters pass by on their way to Arizona schools every day. The mother of two grown children, her heart goes out to them. "I think that all children should have the right to a good education, no matter where they live," says Ms. Johansen. "These kids are our future, on both sides of the border."