Calvert Hall College High School Principal Louis Heidrick will be retiring from his post at the end of the 2012-2013 school year.
"I obviously have mixed emotions about leaving," he said. "But it's a good time, the school is in a good place."
Heidrick was first employed at the Towson boys' preparatory school in September 1965 as a social studies teacher. He was named principal in 2001 and has also served as assistant principal for student affairs, and academic affairs.
The 69-year-old said he has no definite plans post-retirement but hopes to spend more time fishing.
"I have a place by the river," he said.
Calvert Hall has started the process of finding Heidrick's replacement.