Mary O'Neill Rush, 45, a Capitol Hill teacher, community volunteer and resident, died May 18 after collapsing on the playground of Watkins Elementary School, where she taught.

The D.C. medical examiner's office determined that the cause of death was hypertensive and valvular cardiovascular disease.

Mrs. Rush had taught first grade at Watkins for the past eight years. Before that, she served for a decade as director of River Park Nursery School.

Jennifer Smith, the principal at the Capitol Hill Cluster Schools that include Peabody and Watkins elementaries and Stuart-Hobson Middle School, said that Mrs. Rush was always willing to try new things to engage her students. She often incorporated media, parents and other community people in the teaching process.

She also housed an assortment of animals -- gerbils, rabbits, hermit crabs and fish -- in her room for the children's learning and enjoyment. She used riddles and humor, sometimes snaring the principal in her class's antics.

"Her strongest area was writing," Smith said. "She really worked on developing writing skills in the children, from the point where they were just beginning to make letter strings" to where they were writing cryptic sentences. Mrs. Rush oftentimes was the only one who could decipher the sentences, Smith said.

Mrs. Rush, a Capitol Hill resident since the early 1980s, was a familiar figure at community events. She served as a leader for Girl Scout and Boy Scout troops and the Cheverly Swim Team.

Mrs. Rush was a member of Capitol Hill Presbyterian Church. She raised funds for Kingsbury School, Wilson High School and the Capitol Hill Cluster Schools. She was considered a mainstay of the organizing committee for the Capitol Hill Classic, an annual race benefiting the cluster schools.

Mrs. Rush was born in Wilmington, Del., and graduated from Catholic University in 1980. She received a master's degree in education from Trinity University.

Survivors include her husband of 19 years, Andy Rush, and three children, Helen, Jack and Daniel Rush, all of Washington; her parents, Eugene and Geraldine O'Neill of Wilmington; a sister; and a brother.