As of 2019,[update] San Marcos High School enrolls 2,043 ninth through twelfth grade students from a diverse variety of economic and ethnic backgrounds from the Santa Barbara community.

In order to graduate, students are required to complete a minimum of 220 units/credits and to pass the California High School Exit Examination.

Weighted grades are given in Honors, AP and Dual Enrollment courses, the most rigorous classes offered at the school.

English, Calculus, Statistics, Spanish Language, Environmental Horticulture, Latin, Professional Development, Certified Nursing Assistant, Medical Terminology, Marketing (Entrepreneurship) and Auto classes are also offered on campus as Santa Barbara City College (SBCC) dual enrollment courses.

San Marcos has numerous student-led clubs and organizations, including 56 male and female interscholastic sports teams.

The video production class produces daily features and an award-winning weekly 10-minute news and entertainment program.

The leadership program consisting of ASB and Class leaders puts on 3 school dances (homecoming, winter formal, and prom) and implements new ways to make SMHS a better place.

Link Crew consists of about 80 juniors and seniors who lead groups of 10 incoming freshmen during their first quarter of high school.

All students are required to participate in two years of directed school activity such as athletics, drama, band, choir, or physical education.

In recent years benefit concert headliners have included Andy Grammer , Need to Breathe, and Gavin Degraw.

The San Marcos logo originated from the head football coach in 1970, Satini Puailoa III's father.