"Both personally and professionally, my years here have been more rewarding than I can possibly say," he said in an email to the parents of students who attend the private, coeducational college prep school. About 800 students attend middle and high school grades.
Mr. Colb, who is 68, said his plans are still taking shape, but retirement will enable him and his wife Susan to spend more time with family — "on four continents!"
Completing a book on the challenges facing American education and "pursuing a host of interests that have been calling out to me for quite some time" are also on his retirement agenda, he said.
The school has already appointed a search firm and formed a committee to search for a successor, he noted.
Meanwhile, for the next 18 months, he said, "I mean to be as active as ever."
Mr. Colb, who has served as Menlo's head of school since 1993, began his career as an English teacher in the Brookline, Massachusetts, public schools, later becoming the district's director of English and language arts.
He then served in the Newton, Massachusetts, public schools as assistant superintendent for curriculum and instruction. In the 10 years before coming to Menlo, he was the superintendent of schools in the Mamaroneck, New York, public schools.
He received a B.A. degree from Brandeis University in 1964 and an M.A.T. degree from Harvard University in 1965.
He has served on the boards of several nonprofit organizations, including the Independent Records Bureau, the California Association of Independent Schools, and the Reader's Digest Educational Foundation.