The three women were the top vote-getters in a race that drew four contenders, including Ana Uribe-Ruiz.
Ms. Thygesen's newcomer status is qualified by the fact that she served two previous terms on the board — from 2000 to 2008 — before taking a break.
The latest vote count is: Ms. Rich, 4,405; Ms. Thygesen, 3,714; Ms. Lambert, 3,662; and Ana Uribe-Ruiz, 2,248.
Although her children are now adults, Ms. Rich said she wanted to serve one more term to see some key projects through to completion, among them the rebuilding of Hillview Middle School.
In addition to her prior service as a board member, Ms. Thygesen was active in parcel-tax efforts to raise money for the district, and has served on the Menlo Park-Atherton Education Foundation board.
Ms. Lambert will begin her first term on the board next month. She has been an active volunteer in three of the district's four schools, as a board member of the nonprofit school foundation, and as one of the leaders in the Measure C parcel tax campaign.