Margaret M. Ernst, a special needs advocate and former senior vice president of HGI Realty, died Sept. 26 at her home in Washington. She was 56.

The D.C. medical examiner’s office said determination of the cause of death was pending further tests.

Mrs. Ernst moved to Washington in 1988 and began working for what was then McArthur/Glen Realty Corp. of McLean. She helped develop and expand the company’s outlet retail business nationally and internationally before retiring as a senior vice president in 1996.

Her daughter Madeline, who was born in 1995, had significant developmental delays, and Mrs. Ernst became an advocate for children with special needs.

She was appointed by the U.S. secretary of education as a parent representative and board member of the Federal Interagency Coordinating Council, which coordinates federal services for children with disabilities. She was also a member of a steering committee for the U.S. Department of Education’s Office of Special Education Programs and a member of the D.C. State Advisory Panel on Special Education.

Margaret Mary Ernst was born in Buffalo. She received a bachelor’s degree in history from Yale University in 1980 and a master’s degree in business administration from Harvard Business School in 1988. She was a co-founder of the varsity women’s soccer team at Yale, her husband said.

Mrs. Ernst was a commissioner of the D.C. Stoddert Soccer League, the largest youth soccer group in the District. She also helped spearhead an expansion of the Oyster Bilingual Elementary School’s dual-language-immersion program from Woodley Park into Adams Morgan to create the Oyster-Adams Bilingual School, which has a campus in each neighborhood.

Survivors include her husband of 22 years, Frederick Jenney, and two children, Madeline Jenney and Matthew Jenney, all of Washington; two sisters, Julia Ernst of Washington and Mary Kathleen Ernst of Palm Beach, Fla.; and three brothers, Timothy Ernst of Silver Spring, John Ernst of Longmeadow, Mass., and Christopher Ernst of Boulder, Col.

— Megan McDonough