MEXICO CITY (REUTERS) - You're never too old to learn: Mexican grandmother Manuela Hernandez has finally graduated from primary school - at the age of 100.

Born in the southern Mexican state of Oaxaca in June 1913, the year before World War One began, she left primary school after just a year to help her poor family with household chores.

Ms Hernandez only resumed her studies in October at age 99 at the recommendation of a grandchild, and she was handed her diploma at a celebration on Saturday.

"I liked school very much, but I could not continue studying," she told Uno TV. "By the next year I could already wash and iron." Ms Hernandez will continue her studies in secondary school.

More than half of Oaxaca state residents older than 15 have not completed primary education, the second-highest rate in the country behind neighbouring Chiapas, a state education official said.