[2] He and his wife, Mary Margaret (née Ahern), had four children including William P. Barr (who served as the 77th U.S. Attorney General in the George H. W. Bush Administration and as the 85th U.S. Attorney General in the Donald Trump Administration)[3][4] and particle physicist Stephen Barr.

He initiated the Columbia University Science Honors Program in 1958 and was its director (as an assistant dean at the School of Engineering) until 1964.

[9] For a brief time, at the end of his tenure as headmaster, disagraced financier Jeffrey Epstein was employed as a math teacher.

[10][11] In 1973, Barr published Space Relations, a science fiction novel about a planet ruled by oligarchs who engage in child sex slavery.

In 1983 President Ronald Reagan nominated Donald Barr to be a member of the National Council on Educational Research.