The Board of Trustees is comprised primarily of parents and guardians of students enrolled at GMS. Board meetings are held monthly at the school and are open to all families. The Board runs three all-school meetings per year: parent orientation in August, a mid-year status meeting in January, and a meeting in May with information about the coming year.

Much of the Board's work is carried out through committees who report back to the full board: The contracts committee, the finance committee, the strategic planning committee, and the executive committee are among the committees currently in operation. Most of the day-to-day decision-making is delegated to The GMS Head of School, who oversees the teaching and administrative staff.