In Mexico, high school students often have the opportunity to take additional courses on Saturdays, especially if they are part of extracurricular programs or specialized workshops. Among the courses you listed, music is the most likely to be offered as a Saturday class, as it's common for schools to have music programs that may meet outside of regular school hours.
However, English, math, and history could also be offered in special programs or tutoring sessions on Saturdays, especially in preparation for exams or for students seeking to improve their skills.
In summary, music is the most typical course you would expect to encounter on a Saturday, but English, math, and history could also be possible depending on the school's offerings.