"Enough school," she told 15-year-old Aine one day after coming in from the family's small farm. "It's time for you to get married."
That night, Aine lay in their hut on a dank foam mattress, stared up at the thatched ceiling and cried for hours. Then she reached the hardest decision of her young life: She would refuse marriage and demand to stay in school.
To resist, however, often requires bravery beyond a girl's years.
In this poor southern African nation of palm trees and farming villages, more than half the girls marry before they're 17, according to national health surveys; nearly one in five do so before 15.
The practice troubles researchers, who've found that girls who stay in school through their teenage years bear fewer and healthier children, reduce their susceptibility to childbirth injuries and are more likely to give their children more education.
For Aine, the advantages of staying in school were less abstract.
"Why would I want a husband?" she said, perched on a grass mat outside her mother's mud-brick hut one recent afternoon, her soft voice curling into a snicker. "You find the man can't read; he's drinking every day. I would be busy with children all day or stuck farming. It's not a good life."
The sixth of nine children, Aine watched her older sisters marry in their late teens and quickly become pregnant. After her father passed away several years ago, the family's finances shrank, and the hillside plot where they grew maize, cassava and sweet potatoes slowly seemed to wither.
Still, she remained focused on her studies, and when she completed seventh grade last year with near-perfect attendance, the principal encouraged her to enroll in the nearest secondary school, a two-hour drive away. Only 16 percent of Mozambican girls make it that far in school, but Aine had begun to think about becoming a teacher.
That was when her mother told her she had to drop out.
"I was shocked," Aine said, her voice fading to a near-whisper.
"Donors have almost exclusively focused on the primary level. Yet what survey data shows is that getting more than six years of education seems to be a critical threshold for girls having and making different life choices."
Many families also associate schools with immorality and fear that girls will be sexually assaulted or become pregnant outside of marriage, activists said. Girls who are deemed "spoiled" commonly fetch lower bride prices or ruin their chances of marriage.
"As long as she knows how to read and write, what else does she need?" said Aine's brother Basilio, who helps tend the family's crops. "We paid for her school until seventh grade. Now we're tired, and I have my own children. It's better she had a man to look after her."
Many Mozambican girls opt for the security of marriage. Last year, 16-year-old Veronica Candrinho, round-faced and petite, married 25-year-old Jove Moises, a handsome shopkeeper who tooled around Derre on a blue motorcycle.
Veronica's parents had struggled to provide for her, the fourth of seven children, while Moises already had built his own tidy, one-room house off the main road, which she often passed on her walk to school.
"We were too many children at home," Veronica said. "When I was at school, I noticed the other girls had good clothes, books — things I didn't have. So when this guy came around and started giving me things, I felt good."
After they were engaged, she dropped out of school, having just finished seventh grade. As she spoke, she gingerly rubbed her belly: She was nine months pregnant. Hours later, she delivered their first child, a girl.
Aine had other ideas. With help from the local World Vision office, which provided her books and uniform, her family reluctantly scraped together the money for her eighth-grade year. When she returned home in November, her mother said she'd accepted her daughter's decision, although Aine wasn't convinced.
Of the 110 students in Aine's class, 10 are girls. In that little cohort she's found a support group, friends to study and commiserate with. Each fought her own private battle to get there, and along with a few female teachers, they've persuaded Aine that staying in school could be the best thing for her family, too.
"I think I can get a job that would help my mom," she said, "not just staying with farming, but something that pays me well because I have an education."
She straightened her black-and-white top and walked over to the hut where her mother was standing. Both stood with their arms at their sides, the distance between them unspoken but unmistakable.