For more than 100 years, San Marcos Academy has provided a distinctive leadership development program rooted in the values, traditions, and discipline of the United States military. Through the SMA Corps of Cadets, students develop character, responsibility, self-discipline, and servant leadership while participating in a structured environment that encourages personal growth and accountability.

Upper School cadets enroll in credit-bearing Military Leadership courses that follow the curriculum of a Junior ROTC program. These courses are taught by LTC David Jaillite, U.S. Army (Ret.), former Director of the U.S. Army Logistics University. Students earn Junior ROTC credit on their transcripts and may be recommended for appointments to United States military academies. Whether pursuing military service or civilian careers, cadets gain leadership skills and life experiences that prepare them for success beyond graduation.

The Student Council serves as the voice of the student body and promotes active student involvement in the life of San Marcos Academy. Through collaboration with school leadership, Student Council members advocate for student interests, provide valuable feedback, and help foster a positive school culture.

Student Council also plans and coordinates a variety of campus events, activities, and service projects that strengthen community and school spirit. Through leadership opportunities and hands-on experience, members develop communication, teamwork, problem-solving, and servant leadership skills that prepare them to make a meaningful impact both on campus and beyond.

The Robotics program challenges students to apply science, technology, engineering, and mathematics (STEM) concepts through hands-on design, building, and competition. Students work collaboratively to solve complex problems, develop innovative solutions, and compete against teams from across the state and nation. Through Robotics, students cultivate creativity, critical thinking, teamwork, and technical skills that prepare them for future academic and career opportunities.

The National Honor Society recognizes high school students who exemplify excellence in scholarship, leadership, service, and character. Members are selected based on their academic achievement and commitment to serving both the school and community. Through service projects, leadership opportunities, and personal development experiences, NHS members strive to make a positive impact while modeling integrity and excellence.

The National Junior Honor Society celebrates middle school students who demonstrate outstanding achievement in scholarship, leadership, service, character, and citizenship. NJHS encourages students to pursue academic excellence while actively contributing to their school and community. Members participate in service initiatives and leadership opportunities that foster personal growth and responsible citizenship.

Dorm Council provides boarding students with opportunities to develop leadership skills while enhancing residence hall life. Members serve as representatives for their peers, helping to communicate student ideas, organize activities, and promote a positive living environment. Through service, collaboration, and leadership, Dorm Council helps create a strong sense of community among boarding students.

Student Ambassadors serve as representatives of San Marcos Academy, welcoming prospective students and families and sharing their experiences with the SMA community. Ambassadors assist with campus tours, admissions events, and special programs while developing leadership, communication, and hospitality skills. Their role is vital in helping visitors experience the warmth, culture, and mission of the Academy.

The International Thespian Society is an honor organization that recognizes student achievement and excellence in theatre arts. Members are dedicated to developing their talents in acting, technical theatre, directing, and production while promoting the performing arts within the school community. Through performances, competitions, and service opportunities, students grow in creativity, collaboration, confidence, and artistic expression.