Ethel H. Grubbs, 86, a retired supervising director of mathematics in the D.C. public school system, in which she worked for 38 years, died of congestive heart failure Tuesday at her home in Washington.

Mrs. Grubbs, who was born in Washington, graduated from the old M Street High School in 1911 and from Howard University, where she took a bachelor's degree in mathematics, in 1915. From 1917 to 1923, she taught in Fredericksburg, Va., and Petersburg, Va.

She then returned here and began her career in the D.C. public schools.She taught mathematics and physics at Dunbar and Armstrong high schools. In 1927, he was appointed head of mathematics in the black segment of the system, which was segregated at that time. In 1958, she was appointed supervising director of mathematics for the entire school system, which by then had been integrated. She held that post until her retirement in 1961.

In the course of her career, Mrs. Grubbs earned a master's degree from the Teachers College of Columbia University in 1924 and spent 1928 and 1929 studying at the University of Berlin, Germany, on a fellowship she received from the Alpha Kappa Alpha Sorority. She took further graduate work at Howard and other schools.

Mrs. Grubbs was a life member of the National Education Association, the American Teachers Association and the NAACP. She was a member of the D.C. Education Association, the Columbian Education Association, the National Association of Secondary School Principals, D.C. Teachers of Mathematics, the American Association of School Administrators, The Roundtable, the College Alumnae Club, the National Association of College Women, the Retired Teachers Association, the American Association of University Women and the Howard University Alumni Association.

In addition, Mrs. Grubbs was a member of the American Bridge Association and the American Contract Bridge League.

Her husband, William E. Grubbs, whom she married in 1930, died in 1936.

Survivors include a niece, Ethel C. Lewis, whom Mrs. Grubbs raised from the age of three, of Falls Church, and one stepdaughter, Marie Ortiz, of Washington.