But in the years she spent nurturing the children of affluent families in top local preschools — and parenting her own — the thought kept nagging at her: "So many children are not getting that excellent start; it's just a crime."
Armed with little more than her experience and a belief in the transformative power of high-quality preschool, Thomsen is now seeking a venue to launch a mixed-income preschool like no other.
"Kelima" — meaning "all five" in Indonesia, where Thomsen once studied and taught — would start from birth and go to age 5, offering a full-day program along with a high dose of parent participation and education.
"At no other time in a person's life does the brain develop as rapidly as during the first years," wrote David Kirp, author of "The Sandbox Investment," a book Thomsen carries in her tote bag to share with anyone who will listen.
Even as scholars have documented the lasting advantages of high-quality preschool, Thomsen — who taught for many years at Stanford's Bing Nursery School and Menlo Atherton Cooperative Nursery School — observes what she views as a growing "opportunity gap" for local babies.
"I just see the socioeconomic divide in this community becoming greater and greater, not less and less," she said.
"The more I learn about that divide, the more I see that early childhood education is a great opportunity for parents to get together and see that children aren't that different.
"And the return on investment for early childhood education is just indisputable."
Thomsen rattles off the data: Low-income kids with quality preschool experiences "went to prison less, committed few violent crimes, stayed married longer, got married, stayed in high school, went to college more frequently — everything on the average life matrix of success, and not becoming a 'problem' to society," she said.
As of 2009, California spent more than $47,000 per prison inmate per year, according to the state Legislative Analyst's Office. The $20,000 price of a quality, full-day preschool is a better the investment, she argues.
She's scouring for funding and for the right venue — with plenty of natural outdoor space and easy to reach from both sides of U.S. Highway 101 — to launch a mixed-income pilot program with 24 children in fall 2013.
Thomsen's own two sons were born during the 10 years she lived year-round at Stanford Sierra Camp at Fallen Leaf Lake, where her husband, Chris, was director until 1996. When the family returned to the Palo Alto area, her younger son went through Bing Nursery School.
As for her older son, who lived in the mountains through age 5, she said, "I like to think he had me as a teacher."
She takes inspiration from her mother, a social worker whom she used to accompany to prisons, and her grandmother, who founded a preschool in Massachusetts that still operates today.
"When I think about why I'm doing this, I think they instilled in me the idea that with privilege comes responsibility," she said. "Anybody who got to go to Stanford University and have a good education is a privileged person.
"Whether you're an introvert or an extrovert, the social skills you learn in a high quality preschool — how to learn, that the world is an exciting and interesting place that you can trust, to have the confidence to go out and get it — those skills will carry you for the rest of your life."