Mexico City, Mexico - Efigenia Martínez said it was one of the biggest mistakes of her life to bring her grandson Javier back with her to Mexico.

"They treat him like a foreigner but he’s Mexican, he's from here. They've made it so difficult for him to study. I feel like they are discriminating against us."

Efigenia has cared for her grandson since birth and when he was nine she took him illegally to Los Angeles. He crossed the border in a car with a smuggler and then when she knew he was safe, she followed in the back of a trailer.

It was her third illegal crossing. For five years they lived with some of her other children and grandchildren in San Fernando. Despite his illegal status, Javier had no problems enrolling in a US school.

He was a good student and was about to start high school when Efigenia's husband got sick and they came back to Mexico.

It was then that Javier's education problems began. Despite a visit to the Mexican consulate in Los Angeles to get Javier's documents in order, the director of her local school in Cuautepec north of Mexico City said they wouldn't admit him without proof of what grade he had completed.

"I thought because he's from here it would be easy to get him into a school, but it was easier in the United States. Here they asked for many things," Efigenia told Al Jazeera. "They said his classes in the US weren't valid. I was sent all over the city dozens of times to different authorities."

In the end, after almost six months, they had no choice but to enrol Javier as an "oyente" - or unofficial student. He was allowed to go to classes to listen but he wasn't the school's responsibility and wouldn't receive any qualifications.

It's a familiar tale for thousands of children - originally from Mexico or born in the US to Mexican parents who return to Mexico after having studied in the US.

Outside the system

According to migrant rights' groups, the full number of children stuck in this bureaucractic limbo is not known.

Gretchen Kuhner of Instituo para las Mujeres en la Migración (IMUMI) says the issue is ongoing.

"There are more and more kids facing this situation because of the number of deportations and many are coming back to Mexico for economic reasons," she said.

The 2010 Mexican census identified 597,000 US-born children living in Mexico. The next census, out later this year, is expected to see a significant rise in those numbers.

Children need birth certificates and documents that prove their level of education, and they have to be translated and stamped in such a way that the Mexican authorities accept them.

But parents are left to their own devices to navigate a complex situation, said Kuhner.

"They don't know what to do, and many are afraid of turning to the authorities. And it can be as simple as not having a credit card because they're undocumented or poor. If you have the right network and access to the internet, it's easier, but it can take a year just to get a birth certificate."

The Mexican constitution states that every child has an unconditional right to a free education. But because Mexico signed the Hague convention, certain documents must be legally certified for international use and school directors do not want to break the rules.

Some countries have exempted themselves from this provision but not Mexico, said Kuhner.

"It's a lack of political will - there's no other explanation."

Despite repeated calls, the Mexican Ministry of Education did not comment.

At nearly 19, with poor written Spanish and no certificates, he was told he would need to start his education all over again in Mexico. Ma Elena Ayala, mother of deported student

Access to education is not the only obstacle facing those trying to integrate back into life in Mexico.

At Efigenia's house, recent returnees, many with family still living in the US, meet every week to discuss their problems.

Most yearn to go back north and hope to be granted a visa. Many of the mothers at the meeting describe how without the required papers or identification their children couldn't use Mexican health services.

Patrica Lujano returned because her mother was sick and her family's immigration status was in jeopardy after her husband committed a crime.

Unable to get her two children, aged two and three, into a kindergarten in Mexico City or seen by doctors because their paperwork was not in order, the family moved to another Mexican state with more relaxed rules and paid to fix the problem.

"We could do it because we had the economic means but many can't, leaving them outside the system," Lujano said.

More dangerous life

Ma Elena Ayala's son Hector is one of the most extreme examples. Deported months before he was due to graduate from high school, he had nothing to show for his 15 years in California.

Not only was he unable to complete school in Mexico but as a result his work options were very limited Ma Elena says.

"At nearly 19, with poor written Spanish and no certificates, he was told he would need to start his education all over again in Mexico."

In the end he went to work selling candles.

Conscious of this growing problem, the US embassy in Mexico is trying to ensure those born in the United States get their US passports.

Karin Lang, Chief of American Services in Mexico, told Al Jazeera it is doing what it can to help "this large and very vulnerable population".

"These children face significant challenges in economic, educational, and social integration in Mexico. While the Mexican Constitution guarantees access to education for all children regardless of documentation or immigration status, as a practical matter many children are either not admitted to school or are admitted on a conditional status that precludes them from obtaining certificates of completion.

"Without access to education, children anywhere are at high risk. With these children, this is an issue for both countries. These children are US citizens and they are Mexican citizens."

As for Javier, 16, he dreams of going back to California and studying music. Living back among his cousins, uncles and aunts, adjusting to life in Mexico has been tough.

At school he was made fun of because he sounded American. And on the streets where he lives he still does not feel safe.

"Life here is more dangerous," he says, "people get robbed or killed. The schools here have fewer resources too. There we had playing fields and computers."

When his grandmother, who has since obtained a US visa, last returned to California, he got sick and pleaded that she take him.

Efigenia finally got Javier's documents in order before he completed secondary school, but he still has not received his certificate.

"They've told me they don't recognise his classes in the US, but they've also asked me to pay double," she said.

He left school over a year ago and cannot go back to finish his education without the certificate.

Efigenia, too, dreams of taking him back to the United States legally or illegally, but she said smuggling him over the border again is virtually impossible.

"I want to take him but my children say these days it costs $9,000. It's so expensive. Where can I find that money?"