Donald D. Hammill received a doctorate in educational psychology-special education from the University of Texas at Austin in 1963. He had previously served as a teacher in the Corpus Christi (Texas) public schools and as a speech and language therapist in the Deer Park (Texas) public schools. He earned a certificate of clinical competence from the American Speech and Hearing Association in 1963.
From 1963 to 1965, he held an assistant research professorship at the Institute of Logopedics at Wichita State University in Kansas, where he studied the language problems of children with brain damage. In 1965, he went to Temple University in Philadelphia, rising quickly to the rank of full professor of special education. He resigned from Temple in 1972 in order to return home to Texas.
In 1977, Donald established PRO-ED, an international publishing company, and he serves as its president. Today PRO-ED is one of the major international publishers in the areas of special and remedial education, rehabilitation, psychology, assessment, and speech and hearing disorders. The extensive product line includes tests, teaching and therapeutic materials, books and reference materials, and thirteen journals.