Thompson participated for her area club crew team for four years. She also ran cross-country and played squash for a year. She received two MVP awards in high school. Her club women's lightweight crew team placed second in the US Rowing Youth Nationals in 2005. Katharine graduated with High Honor and was on the Honor Roll her sophomore, junior, and senior years. She is the daughter of Marian and Don Thompson. Katharine attended Stuart County Day School of the Sacred Heart.