Every time a woman who we've agreed to call "Serena" gets into her car to drive, she calls her mother, since she fears she may not return home. She's in the United States illegally, can't get a Massachusetts driver's license, and constantly worries about being arrested and turned over to immigration authorities.

Serena has lived with this fear ever since she and her brother arrived here from Brazil to join their mother 15 years ago. She was hopeful when President Obama announced he would expand a program known as "DACA," Deferred Action for Childhood Arrivals, which lifts the threat of deportation for undocumented immigrants who came to this country as children.  

But Obama didn’t change the age cut-off: DACA is only for people who were under 16 when they arrived. Serena was six months too old.

"I was really hopeful; I was ready; I was making plans," she said. "I was going to go for my social, then my driver’s license, then apply to college." 

For those covered, the executive order offers not only protection from deportation, but also the chance to get a work permit.

"It means a big relief," said Yamila Pastorino, who qualified for DACA and has a license.

Because her brother was born in this country, her parents will be protected from deportation.

"It’s indescribable, the feeling of peace that we get, knowing that they can stay, can work, can do whatever they have to do," she said. 

Tracking the exact number of undocumented residents is by nature an inexact science. But within the estimated 150,000 here in Massachusetts, Yamila and Serena represent a divide created by Obama’s order.

Frank Soults, the communications director at Massachusetts Immigrant and Refugee Advocacy, said the order doesn't solve the country's immigration issue.

"You’re talking about a population cut in half," he said at a press conference. "Half of them getting the benefits to stay, come out of those shadows, and half struggling as they have before." 

Those on the other side of the debate agree. Their concern: Obama’s order places more emphasis on border security and less on immigration violations. That, they say, will in effect lead to widespread protection of all undocumented immigrants.

"Most of the rest of the illegal resident population is going to be exempt from deportation if here before January of 2014," said Jessica Vaughan, the director of policy studies at the Center for Immigration Studies. "It’s not just giving work permits to half the population, but everybody else pretty much get to stay, unless convicted of a felony."

Back behind the wheel of the car she’s not legally allowed to drive, Serena is still looking over her shoulder.     She’s thinking about moving, not back to her native Brazil, but a new state: Illinois, where she can get a driver's license and in-state tuition.

Spanish-language immigrant advocate Patricia Sobalvarro and Center for Immigration policy studies director Jessica Vaughan discussed on Greater Boston what the president's executive order means for a long-term fix to the United States' immigration system: