Gnats swarm his face and sweat beads on his brow.
The mercury reads 88, but with 40 percent humidity, it feels well above 90 and no breeze to offer respite.
Pablo Caballero Sr. bends over and checks the irrigation drip moistening a row of tomato plants. It's 2 p.m. He has been in the field on St. Helena Island nearly six hours and has another four to go.
His hands are worn like old leather -- callused, cracked and tan from decades of picking tomatoes, watermelon and other produce on migrant farms in South Carolina and Virginia.
At 48, his knees throb and his back aches. He's no longer the vigorous, 17-year-old who left his family in Mexico City looking for freedom, work and upward mobility.
He pauses to wipe the sweat from his brow and to check his watch.
His oldest son, Pablo Caballero Jr., should be home soon from his last class at the Technical College of the Lowcountry where he hopes to train as a nurse.
The 18-year-old started classes the week before. After graduating this spring from Beaufort High School, he became the state's first migrant student in six years to earn a high school diploma.
"I feel so proud," his father says through a translator. "The work in the fields is very hard; it's very difficult. I'm proud of myself to be able to raise a family through agriculture. But when I'm very, very tired, I always tell my kids, 'I want something better for you.' ... To see him realize his dream ... "
His voice trails off for a moment.
"I have no words," he says finally.
While the dreams he had 31 years ago may not have turned out as he had hoped, Pablo Caballero Sr. can still manage a smile.
The 12-hour days, the work weeks that can stretch into seven days, the knee and back pain -- all of it is worth it, he says. His wife and five children have a better life.
His son has a diploma -- something no one else in his family has ever had and that only a handful of children of migrant workers have accomplished, despite a long-standing program designed to educate them.
"He is the very, very rare exception," said S.C. Department of Education spokesman Jay Ragley. "You found the proverbial needle in the haystack. ... It is outstanding."
Of the 1,439 migrant students documented by the state in 2011-12 -- the most recent year audited numbers are available -- 63 were enrolled in grades nine to 12.
Of those, six were seniors, and none earned a diploma or received a high school equivalency certificate, Ragley said.
While numbers were not available for the 2012-13 school year, "to the best of our knowledge, (Pablo) is the first to get a South Carolina diploma in six years," he said.
Nationally, only about half of all students categorized as migrant students graduate, Ragley said.
Despite federal-supported programs to educate the children of migrants, dropout rates are high and achievement levels low, according to a 2011 S.C. Department of Education report.
The reasons are not too difficult to imagine, Ragley said.
Parents often do not speak English. The transient nature of their work disrupts their school year, making any effective student-teacher relationship short-lived, according to the state report.
Families tend to spend the winter in Florida picking oranges and move north in the spring to pick tomatoes in the Lowcountry before heading to New York in the fall to pick apples.
Then, the cycle repeats.
That means children often struggle to complete a grade, according to Terry Bennett, who oversees Beaufort County's Migrant Education Program. And those enrolled one school year may not return the next, he said.
Of the 275 migrant children served by the Beaufort County School District last school year, 175 were between 16 and 21 and were not in school, Bennett said. Instead, they received lessons in life skills, farm safety, math and English during the evenings or weekends.
The prospect of immediate money lures many into the fields or into other work, Bennett said.
Those who stay in school often are held back and are ill at ease among younger, better prepared classmates, according to the 2011 state report.
Parents also are often unaware of continuing-education programs, arrive after enrollment for those programs has closed or when too little time remains to benefit from them.
Pablo faced many of the challenges so common among those like him; his diploma is a testament to a family's uncommon resolve.
A FAMILY REUNITED
Pablo Caballero Sr., a U.S. citizen, had only six years of formal schooling back in Mexico.
He moved to Beaufort County in 1985 with friends to work in the camps on St. Helena Island. Jobs, he said, were scarce back home.
At the end of the growing season in October, he would return home for a few moths before heading back to the camps in February.
In 1993, he married Ema Caballero-Rodriguez, a homemaker. In 1995, she gave birth to Pablo Jr. Four more children followed, but it would take nearly 13 years to secure the legal documents to bring his family with him to St. Helena.
Before they were reunited, the father fretted for years about his far-away family and his children's future.
His oldest son worried about his well-being, alone in a new country working exhausting hours.
Father and son yearned to see one another.
In 2008, they were permanently reunited, beginning an arduous journey that would find the son striving to live up to the father's dreams.
'WHY WOULD I QUIT?'
A drawing hangs in a bedroom barely big enough for two single beds -- each pushed against a wall to make an "L" -- a small dresser and a closet.
It was sketched by Pablo Jr.'s younger brother, Noè, a junior at Beaufort High with whom he shares the room, and depicts two arms, each drawing the other.
One arm says, "U.S.A."; the other, "Mexico." Between them is the head of a bald eagle, a soccer ball and the American flag.
For Pablo, the drawing symbolizes a promise fulfilled and a commitment he cannot break.
No matter how difficult the assignment, no matter how boring the task, no matter how tempting the distraction, school comes first. Period.
His mother and father make sure of that.
Each child gets a half-hour to relax after school. Then, it's time for homework, dinner and tutoring at the Franciscan Center on St. Helena. Pablo also volunteers there along with Noè, helping run its thrift store and assisting kindergarten and first-grade students with homework and vocabulary.
"When we first moved here, I didn't know any English," Pablo said. "The only thing I knew how to do was math, because it's numbers. Everything else -- English, science -- I didn't know what I was doing."
It wasn't until his sophomore year that he became proficient in English, thanks to help from Rosetta Stone, bilingual teachers and volunteers at the center who teach English to Hispanic and Latino community members. He also had help from a fellow Hispanic classmate who translated classroom work.
"It took a lot of patience," Pablo said.
But patience wears thin. There were times when he was discouraged and frustrated.
Then he would think of his dad, of how exhausted he looked coming in from the fields.
"If he brought us here to become someone in life, why would I quit and become nothing?"
He wants to be a role model for his siblings, showing them -- as his father does in the fields -- what can be achieved through determination and perseverance.
"I know they're looking up to me," he says. "... My brother wants to be a firefighter, and my sister (a sophomore at Beaufort High) wants to be an artist, and as the older brother, I want to show them" they can do that.
A BETTER LIFE
Pablo kicks dirt as he takes a walk around the fenced-off Lipman Produce camp. The company employs about 4,000 workers in 22 locations throughout North America -- researching, growing, packing and distributing produce, primarily tomatoes, according to the company's website.
In June and July, at the peak of picking season, hundreds of migrants descend on the camp.
A handful, including Pablo's father, work there year-round, staying with their families in the trailers that dot the camp. The rest, mainly seasonal workers, stay in one-story buildings resembling small motels. They sleep four or five to a room, each with a bathroom and a small, communal kitchen in the middle.
At the end of the grass yard sits a brick building with a concrete floor that houses four stoves, two sinks and two plastic picnic tables.
This has been Pablo's home for nearly five years.
He often felt the urge to join his father in the fields. He admires his work ethic and felt he could do more for his family picking tomatoes than solving math equations.
But his father made one thing abundantly clear: Pablo's life would be different. He was to have a better one.
His father's desire was reflected in the stable home he provided for his children, Bennett said. They have made the St. Helena camp their home base. While other migrant children move from camp to camp throughout the school year, the Caballero family largely stayed put.
During the summer, they move for a few weeks for work in Virginia, but always return in time for school.
Because the family moves, they qualify for the migrant education program.
Under federal law, to be classified as a migrant a child has to have moved within 36 months for temporary or seasonal farm or fishing work or have accompanied a parent or guardian seeking such work.
"Pablo's parents need to be commended for holding education in such high regard for their children, instilling in them that they need to get a quality education first," and doing what was necessary to provide that, said Liza Santiago, a family services liaison with Beaufort County's Migrant Education Program.
"Pablo and his family are examples for the whole community. And we are so very proud and blessed of what he's reaching. We hope more will follow his lead."
And make the dream of education -- and a better life -- a reality.
Follow reporter Tom Barton at twitter.com/IPBG_Tom.