New Athletic Director Announced

Following a comprehensive, nationwide search, Sean Lissemore has been selected as St. Mark’s next Athletic Director and will assume his new responsibilities on July 1. Sean comes to St. Mark’s following a successful seven-year career in the National Football League as a defensive lineman for the Dallas Cowboys and the San Diego Chargers.

“From our first conversation with Sean, it was evident that he cared deeply about helping every student-athlete realize his personal, academic, and athletic potential,” said Associate Headmaster John Ashton. “Sean joins a highly experienced leadership team, and we are excited about the important contributions that he will make to the strategic direction and advancement of the School’s mission.”

An exceptional scholar-athlete who made an impact on and off the field, Sean enjoyed a successful high school career, where he excelled in football, wrestling, and track and field. He went on to become a standout collegiate football player at the College of William & Mary, majoring in kinesiology, serving as team captain, and earning All-American honors. At the end of his college career, Sean was drafted into the National Football League where he spent three years playing for the Dallas Cowboys and four years with the San Diego Chargers. During his seven-year professional career, Sean played in 69 games and registered 135 tackles, one interception, and one touchdown.

Eugene McDermott Headmaster David Dini noted his enthusiasm for the appointment saying, “Sean brings a passionate commitment to athletic excellence, and, more important, he shares our commitment to helping shape every boy’s character in positive and meaningful ways. Sean is confident yet humble, competitive yet kind, and will serve as a great role model for our boys.”

In addition to his accomplishments as a professional athlete, Sean earned a Master of Science degree in Strategic Management and a Graduate Certificate in Business Management from Indiana University. He also received a Graduate Certificate in Business Management from William & Mary’s Raymond A. Mason School of Business and a Graduate Certificate from the NFL Business Management and Entrepreneur Program at the University of Pennsylvania’s Wharton School. Since 2015, Sean has been a member of the United States Coast Guard Auxiliary, where he is a Communication Services Staff Officer.

Throughout his career in the NFL, Sean was actively involved in contributing to the betterment of his community, with a particular passion for youth development and education. He founded and organized the Sean Lissemore Youth Football Camp, a free enrichment program for children in his hometown of Dumont, New Jersey. While certainly a humble servant leader, Sean has been recognized for his extensive volunteer involvement, including being named the San Diego Charger’s NFL Military Salute to Service Nominee.

Sean succeeds Mark Sullivan, who served as St. Mark’s Director of Physical Education and Athletics for the past 20 years and managed 88 coaches, 500 annual athletic contests, and 45 teams across 16 sports. During Mark’s two-decade tenure as Athletic Director, St. Mark’s teams won 77 Southwest Preparatory Conference Championships, 16 Regional Championships, and 16 State Championships, and the School was recognized with the SPC Director’s Cup Trophy as the winningest boys’ athletic program 11 of the past 13 years.

“From the minute I stepped foot on campus, it was evident that this school is a very special place,” Sean said. “The culture at St. Mark’s is built on a strong foundation of character, integrity, work ethic, and respect. I look forward to building relationships with all of the talented student-athletes, faculty, staff, and coaches at St. Mark’s, and I hope that my experience will bring additional value to an already outstanding athletics program.”

Sean will work closely with Associate Athletic Director Josh Friesen to oversee the School’s varied sports programs across the campus. As is noted in Goals for St. Mark’s IV, there will be continued focus on the evaluation and further strengthening of all athletic programs to contribute to the holistic experience of every student.

Sean and his wife Chelsea are the parents of a two-year-old son, Jack.

St. Mark's School of Texas

10600 Preston Road
Dallas, Texas 75230


About Us

St. Mark’s School of Texas is a private, nonsectarian college-preparatory boys’ day school for students in grades 1 through 12, located in Dallas, Texas. St. Mark’s aims to prepare young men to assume leadership and responsibility in a competitive and changing world.

St. Mark’s does not discriminate in the administration of its admission and education policies on the basis of race, color, religion, sexual orientation, or national or ethnic origin.