Randy Tucker, who has served as headmaster of GPS for 26 years, will retire June 30.
"After long consideration and with the support of the Board of Trustees, I have decided to retire in June 2013 as opposed to June 2014," Tucker wrote in an email Wednesday to alumni, parents and faculty.
He acknowledged that hiring a new head of school can be difficult after the tenure of a long-serving leader.
"To that end, I have decided the best course of action for GPS is for me to retire early and allow the Board to put an Interim Head of School in place for the academic year 2013-14," he wrote.
In the email, Tucker said the board would select an interim head of school who would be in place by the time he retires at the end of June.