John A. Lavan, 56, a rehabilitation services adminitrator for the Department of Education and its predecessor agency, the old Department of Health, Education and Welfare, died of cancer Sunday at his home in Alexandria.

Mr. Lavan began his 21 years with HEW and the Department of Education as a budget examiner for the Public Health Service. He later served as HEW's chief of plans, projects and grants for vocational rehabilitation and as executive officer for HEW's social rehabilitation services administration, which was transferred to the Department of Education when it was established last year.

A member of the board of directors of HEW's federal credit union since 1971, Mr. Lavan had been credit union chairman and was its president twice.

He was born in New York City and earned a bachelor's degree in accounting and finance from Iona College in New Rochelle, N.Y. He earned a master's degree in economics from Catholic University.

Before moving to Alexandria in 1953, Mr. Lavan worked for the National Broadcasting Co. in New York City. He was comptroller and business manager for NBC here before joining HEW in 1959.

Mr. Lavan was a member of the Metropolitan Washington Health and Welfare Council and the Urban League. He served on an ad hoc commission on consumer affairs for the city of Alexandria and as a financial adviser to the Hospice of Northern Virginia.

Survivors include his wife of 27 years, Mary G., and a son, David J., both of Alexandria; another son, J. Andrew, of Annandale; a daughter, Noreen Ann, of Washington; a brother, Thomas, of Point Pleasant, N.J., and a sister, Kathleen Sullivan of Brewster, N.Y.

The family suggests that expressions of sympathy be in the form of contributions to the Hospice of Northern Virginia in Arlington.