David Runkle joined Rivers as an Upper School math teacher in 2020. He has a BS in mathematics from Elon University and an MS in mathematics from UNC-Chapel Hill. David has taught high school math in North Carolina and directed educational programming in yoga schools in Minnesota, Florida, and Massachusetts.

Elizabeth Wendorf, math department chair, is a seasoned teacher of Upper School mathematics.  A graduate of Wesleyan University with both a BA and an MA in mathematics, Elizabeth loves sharing her passion for the subject with her students. Before joining Rivers, Elizabeth taught high school mathematics at Kent School in Connecticut. She was also a teaching assistant at Wesleyan. In addition to teaching, Elizabeth runs the math teaching assistant program for seniors and supports the venture capital competition club. She also coaches the varsity ski team and girls' soccer.

John Adams joined the Rivers math department in 2015. Prior to his career in education, he worked in finance and sales at the CEB (now Gartner). His work in schools began at The Dublin School, where he served as the math department chair, dorm head, and head varsity lacrosse coach. In addition to teaching math at Rivers, John has served as the director of academic technology and coached varsity XC skiing and JV boys’ lacrosse. During the pandemic, John spearheaded the Rivers’ digital transformation and won the 2021 Walter Family Community Prize for his efforts. John received a B.A. in economics from Bates College, where he captained the lacrosse team. As director of technology and innovation, John oversees all aspects of technology integration, infrastructure, and strategic planning, aiming to build strong, collaborative relationships with various stakeholders to ensure technology effectively supports the school’s mission and educational goals.

Jean joined the Rivers community in 2024. She teaches Upper School mathematics and serves as the assistant coach for the JV girls’ ice hockey team. She has a B.A. in mathematics from Hamilton College and an M.Ed. in secondary school mathematics from Boston University. Before moving to Boston to earn her master’s degree, Jean taught mathematics and coached at New Canaan Country School in Connecticut. While at Hamilton, Jean was a member of the varsity squash team. She enjoys reading, cooking, skiing, and being outdoors.

Mary Carroll graduated from Carleton College with a B.A. in mathematics and earned an M.L.S. from Reed College. She has taught in Costa Rica, Turkey, Spain, and the Dominican Republic as well as the United States. After several years abroad, Mary returned to her home state of Massachusetts in 2015. Prior to joining Rivers in 2024, she worked at CATS Academy Boston, where she taught across the curriculum and served as department chair.

Matt Dias Costa, a Rivers graduate, spent two years teaching algebra and precalculus at The Taft School, where he was a Penn Fellow in mathematics, before coming to Rivers. At Rivers, Matt teaches ninth and tenth grade math. Matt graduated from Bowdoin College with a BS in mathematics and earned an MS in education at the University of Pennsylvania. While at Bowdoin, he was a four-year varsity soccer player and was named most valuable player and varsity team captain in his senior season. Matt serves as assistant coach for boys' varsity soccer at Rivers.

Kristin Harder came to Rivers in 2003 and served as the math department chair and girls' varsity hockey coach until 2011. She currently teaches Upper School math, coaches Middle School girls' hockey, advises in the Upper School, and serves as an Upper School course counselor.

Victoria Mizzi, Upper School dean of student life, joined the mathematics department in 2016 after teaching the IB math curriculum at the International School of Boston and, since arriving, has taught math across the Upper School curriculum, from Grade 9 Geometry with Algebra to the Grade 12 Multivariate Calculus and Linear Algebra sequence. She has also served as grade dean on the Grade 11 and 12 rotation and as a course counselor. Prior to joining Rivers, Victoria worked at the Washington International School in Washington, D.C., where she also served as department chair. Victoria received both a B.Ed. and a B.S. from Queen’s University, Ontario, and has since been a learning group fellow at Project Zero Classroom at Harvard’s Graduate School of Education, as well as a learning group facilitator and mini-course leader at the Washington International School Summer Institute for Teachers in Washington, D.C.

Christine Pynchon is an Upper School mathematics teacher and the head coach of the varsity softball team. She also serves as an Upper School grade dean. She has a BS in mathematics from Colby College, where she played varsity softball. Prior to joining Rivers, she taught upper level math and coached softball and soccer at the Berkshire School after interning at Phillips Exeter Academy.

Alice Sorensen teaches mathematics at the Upper School level and coaches JV field hockey, JV girls’ ice hockey, and JV girls’ lacrosse. She has a bachelor’s degree in psychology from Brown University and an MEd in science and math from the College of Charleston. She taught mathematics and coached at the Lincoln School, Rectory School, and St. Anne’s-Belfield School. While at Brown, she played on the club ice hockey team and also coached hockey in their youth program.

Kim Webster started teaching math at Rivers in 2001. She earned a BA in economics at Williams College, where she played soccer, and an MEd with a specialization in sports psychology at Boston University. A mother of three boys, Kim has been a triathlete for 20 years, competing in several world championship events, including the Ironman in Kona. She also regularly competes in the Boston Marathon. Kim has served as soccer and alpine skiing coach at Rivers, and runs the math TA program.

Keith Zalaski serves as director of athletics and coaches varsity boys’ basketball. He also teaches mathematics in the Upper School. Prior to joining Rivers, he taught at Arlington Catholic, Trinity Pawling, and Williston Northampton School. He has also served as assistant men’s basketball coach at Tufts University. He has a BA in economics from Amherst College, where he played basketball and captained the golf team, and an MA in teaching from Tufts University.