Through the chill of the early morning, they make their way through the border. They come in pairs and in groups, the odd straggler running to catch up.
They chat, and laugh and yawn. For many, the day begins well before sunrise – and they look exhausted before the day has really begun. It normally takes 20 to 30 minutes to make the crossing, but on the worst days it can take anything up to an hour and a half.
Every day, the crossing at Douglas in Arizona sees dozens of children cross from Mexico heading to school in the US. But many shouldn’t be here. They don’t meet the local requirements.
Most are American citizens, born in the US and with a valid passport. But their parents have moved back to Mexico, where it’s cheaper to live, where they have family, where they feel comfortable.
One girl tells me her name is Angel. She’s wearing a light zipped sweatshirt and carries a heavy backpack weighed down by school books. "I’m American. I’m from Arizona and so I have to come here to school."
Luis is her friend and he tells me a similar story: "I was born here so I need to come to school here in the United States."
Many of the children are caught between two worlds and two systems. They tell me if they were born in the US, then schools in Mexico demand payment for schooling. But then if their family doesn’t have residency in Douglas, they shouldn’t be going to school here.
So to give their children the best possible education, many parents bend the rules. Critics say they are essentially stealing an education.
The state of Arizona gives taxpayer money to each school district for each pupil that’s enrolled. It demands one form of identity to prove residency. Douglas now wants three. Sheila Rogers is the Superintendent for Douglas schools.
Sitting in her office, surrounded by papers and charts, she says the checks are to protect the money being given to her schools.
“If we didn’t do our due diligence, the state could come back and if they found we had X amount of students who were not legal residents, they could require us to pay the money back. That has happened in other districts in Arizona,” she says.
Normally in schools in America, children are registered once they start and that’s it. In Douglas, parents have to do it every year. A new student centre has been established to check out claims of all those registering their children.
Bonnie Lopez runs it. Someone who has spent her life in education, she wants children to get the best possible start, but she wants people to follow the rules.
"We’ve had people using addresses that aren’t theirs," Lopez says.
"One couple registered their child in school using the address of the school district office.
"They’ve also used derelict buildings and claimed they lived there. They ask people to allow them to use their addresses and pay for the privilege . And then of course we see fake driving licenses and birth certificates and utility bills that are altered.
"There are many ways to try to scam the system and we try very hard to filter who the true residents are."
Giving fake addresses can also cause problems.
Once a child became very ill at school. The address the parents had given was fake.
Only the intervention of the Red Cross and diplomats on both sides of the border helped track down the parents in Mexico and permission given for medical treatment.
Back at the border a girl who calls herself Maria is waiting, phone in hand, talking quickly in Spanish before waving to some youngsters making the crossing.
"I live here in Douglas and I come early every morning to make sure my cousins come to school because their parents can’t cross," she tells me.
"I have to make sure they make it here safely and get them a ride to school and make sure they’re on time and everything."
I ask if her cousins are registered at her address. She smiles and walks away to shepherd her cousins into waiting cars.
When school’s out, standing at the gates of just one, I count the Mexican licence plates on the cars. It takes me no time to get to 20.
There are some who pay to have their children attend school in the US. And there are private and church schools in Douglas that will happily take their money. But there are others who are willing to take a chance, figuring the risk is worth it if it gets their children a better education, a better future and a better life.