When I started working on my biography of the Italian physician Maria Montessori, I worried I wouldn’t be able to do justice to her personal life. People associate the name Montessori with a style of schooling that lets children focus on their interests, unhindered by the constraints of traditional education. But very little is known about the woman who created the revolutionary educational model.

Maria Montessori, the early-20th-century Italian doctor and teacher, was a distinctly modern woman, both privately and professionally.

At the turn of the last century, women of Montessori’s social class were expected to become housewives. But Montessori never considered conforming to conventions by marrying young and becoming a mother and wife. Instead, in 1893 she enrolled in the University of Rome’s medical school and studied pediatric medicine and psychiatry. After graduating, in 1896, she went on to work at the university’s psychiatric clinic. Within a year, she’d found a cause to devote her career to: the education of handicapped children.

Around that time, Montessori started up a clandestine relationship with a colleague, Giuseppe Montesano. In 1897 she discovered that she was pregnant with his child.

At the turn of the last century, women of Maria Montessori’s social class were expected to become housewives.

Per the social norms in Italy at the time, marriage obliged a woman to renounce her career and work in the home. But Montessori was in the middle of pioneering a new approach to treating handicapped children, the result of many hours of research spent in addition to her day job as a physician. Instead of relegating them to asylums, Montessori was exploring the idea of integrating handicapped children into regular schools. In order to continue her medical research, she decided to give birth to her son, Mario, in secret.

After he was born, in 1898, Montessori entrusted a nurse who lived on a farm near Rome to house him. She still wanted to raise the child, though, and struck a deal with Montesano. They would parent Mario together, secretly, and while they wouldn’t marry each other, they promised not to marry anyone else, either.

This agreement didn’t last long. When Mario was three years old, his father succumbed to pressure from his family and married a woman with advantageous social connections. Just a few days before his wedding, Montesano legally recognized Mario as his son, making him Mario’s only legal parent. Hurt by his betrayal, Montessori severed all ties with Montesano.

To continue her medical research, Montessori decided to give birth to her son, Mario, in secret.

When Mario was seven years old, his father sent him away to a boarding school in Tuscany. Montessori couldn’t see her own son anymore, and it broke her heart.

When Mario turned 15, Montessori decided to take her child back. She wrote him a letter revealing the broken arrangement she had had with his father. Together, Montessori and her son agreed to stage his “kidnapping” during a school field trip. The plan was a success, and Mario went to live with Montessori in Rome. To avoid a scandal, she called Mario her nephew. The two never separated again.

From there on out, Montessori managed to balance motherhood with a successful career, which culminated in her development of the Montessori method, all the rage in the 1910s and still practiced today. Once Mario was old enough, Montessori pursued much of her educational research with him.

Cristina De Stefano is a Paris-based journalist and the author of four books. Her latest, The Child Is the Teacher, will be published on March 8 by Other Press