SOMERVILLE -- Tiphaine Guillabert, the newly minted principal of St. Theresa of the Child Jesus School in Somerville, is a Renaissance woman -- literally.

Her dissertation, researched at Paris's famed Sorbonne (where she also taught) and at the University of Neuchatel in Switzerland, was about the history of pre-Lent Carnival festivities in Early Modern Europe. She's also written a book about the subject, and another entitled "Language and Faith at the Age of Reforms in Europe." European history was her specialty when she taught at Harvard. She wanted to explore the Catholic Church's relationship between the indulgence in pleasure, which Carnival allowed the faithful to revel in, and the renunciation of it during Lent.

"There was a constant dichotomy in the church between an ascetic point of view, the reject, the refusal of the world, of the flesh," she said, "and at the same point, the statement that God was made flesh. So we can't refuse the world. So how do we balance it?"

Guillabert wants St. Theresa's 155 pre-K- to eighth-grade students not to refuse the world. Students perform community service every month, whether it be with senior citizens or firefighters.

"Long term, we are educating students to become citizens, to be part of the community at a larger scale," she said.

St. Theresa's, which celebrates its 100th anniversary next year, is the last Catholic school remaining in Somerville. It's nestled comfortably in the diverse Spring Hill neighborhood, which Guillabert described as a revolving door of residents moving in and out. In the face of change, families and teachers have stayed with the school for generations.

"I think here in the United States, schools are quite open to the public sphere," Guillabert said. "And this is something I think that is interesting for the students, also for the community. We may enrich each other."

Some people she met in the neighborhood didn't even know the school existed. Guillabert wants to change that with a more assertive marketing campaign. When The Pilot visited her office on Nov. 18, pamphlets advertising the school in Portuguese and Haitian Creole were on her desk. Ten languages are spoken among the students. Guillabert herself knows French, German, and English. Written above the PA system next to her desk was a reminder -- today was student Gigi's eighth birthday.

"One of the traits of this school is the family atmosphere," Guillabert said.

She smiled and hugged the first graders she met in the halls, and taught them how to sing the "Agnus Dei" in Latin (among her many talents, she instructs the students how to sing at Mass) and gave them a brief overview of the language's history.

"Don't worry if you don't remember everything right now," she said, "because you will have the spreadsheets at Mass."

Guillabert was born in Tours, France, and had a "simple childhood," marked by a love of reading and culture.

"I discovered a passion," she said. "I discovered my vocation, and along with the desire to serve as a Catholic. So education for me was a wonderful way to do it, because you can serve the students."

She is an archicube (alumna) of the Ecole normale superieure in Paris, the grandest of France's grandes ecoles. She received a master's degree from the University of Vienna and taught at a Catholic school in France. Getting to speak openly about God in such a secular country was enjoyable for her.

"You're grounding your values not in yourself, but something bigger -- God," she said.

Teaching history was her way to introduce children to "the deeper meaning of life." She loved inspiring her students to be more confident. In 2021, she moved to the U.S. with her family to take the teaching position at Harvard. It was tough leaving her friends, relatives, and country behind, but being in New England allowed her to continue her other passion -- skiing. Her father was a pilot in the French Air Force, and she would often visit him in the mountains, where she learned how to ski. She is part of an amateur skiing league in New England, where the cold, hard snow makes the sport more challenging than in Europe. She came in second place last year. For her, skiing is exhilarating and a reminder of home at the same time.

"At first it was tough," she said, "and one thing that put me on track was to ski again, because it's a way to realize yourself and keep to be self confident."

It's like St. Theresa's slogan: "Come to know. Come to BE known."

Like everything else in her life, there's a spiritual side to skiing. Even seeing the sun in her office window reminds her of "the beauty of life."

When the 2025-26 school year began at St. Theresa's, it was Guillabert's first time as a principal anywhere. She isn't used to managing people who are the same age or older than she is. Young teens are "more challenging" to teach than Harvard students, she added. Cultural differences can make things even more confusing. Her devotion to the school's namesake, St. Therese of Lisieux, has given her focus.

"She's the one who made the relationship with God and the perception of saint, of holiness, close to us," she said. "She demonstrated that we could become a saint in our daily life. And this is important for children."

Guillabert likened becoming a school principal to joining a religious order.

"We have everyday challenges," she said. "It's tough. I mean, there is a lot of things going on and being confident that you will be helped."

She added: "It's trying to do your best, not for yourself, but to serve and trying to have good relationships with everybody."

She recently met an 80-year-old donor who attended St. Theresa's in the 1950s. The son of a cleaner, he was disruptive in class until the sisters, who then operated the school, told him, "You can't act like that with your father working so hard." Guillabert admired the sisters' courage and willingness to be frank with him. The man told her that his Catholic education changed his mindset and helped him start a successful business. She won't be able to see what her students become, but she wants to plant the same seed in them.

"It's wonderful to see a school that has a life, has a history like that, and you want to pass it on," she said.