The girl, identified only as Anne Marie, says sex lessons came too late for her.
She delivered an eight-pound boy in September, after becoming pregnant by a 13-year-old boy.
"I went through all the options to decide whether to keep him or not, and I thought if I got rid of him I would regret it later in life," she said.
Her mother, 36, told Anne Marie that the decision was up to her, and offered her full support.
"I thought she would be a lot more sensible than that -- I didn't even know that she had a boyfriend," the mother said.
But the family says sex education in schools is behind the times and should start earlier.
"I think it should have been a bit earlier than it was -- because I was pregnant when I had sex education," Anne Marie said.
Her mother has decided to look after the baby boy while her daughter is at school.