John Leachman Palmer, 66, a former school principal and a retired coordinator of administrative research for Arlington County public schools, died of cancer Thursday at Arlington Hospital.

Mr. Palmer joined the Arlington County school system in 1950 as head teacher of the old John Marshall Annex Elementary School. He was principal of the old Cherrydale Elementary School from 1953 to 1956. He was appointed director of research for the school system in 1957.

A former president of the Arlington Education Association, Mr. Palmer had served as its salary committee chairman and was a member of its executive committee for several years.

Through the association, he worked to improve teachers' salaries. As chairman of the fringe benefits committee of the Arlington Retired Teachers Association, he worked for a cost-of-living provision in the Arlington County School Employes Supplemental Retirement System.

Born and reared in Arlington, Mr. Palmer earned bachelor's and master's degrees in education from the University of Virginia. He also did doctoral work at the university on research techniques.

Mr. Palmer was a life member of the National Education Association, a charter member of the Washington Area Council of Public School Education Associations and a member of both the National and Virginia councils for social studies.

Active in civic and community affairs, he served as treasurer of the Arlington Historical Society and area chairman of Reading is Fundamental (RIF) of Northern Virginia.

In the early 1950s, Mr. Palmer coordinated Halloween parties to raise funds for UNICEF in the Cherrydale area. He also was credited with originating the Optimist Club's junior golf program.

During World War II, he served in (Supreme Headquarters, Allied Expeditionary Forces).

Mr. Palmer lived in Arlington and attended the Second Church of Christ Scientist there. He had also been a choir soloist and organist at several other area churches.

Survivors include his wife of 39 years, the former Ethel Nelson, and a daughter, Karen M., both of Arlington, and a sister, Helen P. Kettler, also of Arlington.

The family suggests that expressions of sympathy be in the form of contributions to the American Cancer Society or to the Second Church of Christ Scientist.