Dr. Stiff has taught mathematics at the middle grades and high school levels since 1971 after completing a B.S. degree in mathematics from the University of North Carolina at Chapel Hill. In May 1978, he received his Ph.D. in mathematics education from North Carolina State University. 

In August 1978, he joined the faculty of the University of North Carolina at Charlotte, where he received the 'Reginald V. Blackmon Award for Excellence in Teaching' in 1980. In 1983, he returned to NCSU, and in 1985, he completed study in computer science from the Institute for Retraining in Computer Science at Clarkson University in New York.  In 1992, he was presented 'The W. W. Rankin Memorial Award for Excellence in Mathematics Education' by the North Carolina Council of Teachers of Mathematics. 

Since returning to NCSU, he has taught courses in mathematics and mathematics education, including methods courses for middle grades and high school pre-service teachers, methods courses in the uses of technology for teaching mathematics, and graduate courses about teaching algebraic reasoning. He has chaired  to completion the committees of nine Ph.D. students in mathematics education, and he has received over $1,000,000 in grants. 

Dr. Stiff has been active in many professional organizations, including the Benjamin Banneker Association, NCTM, NCCTM, AERA, and PME-NA. Most notably, he served as NCTM President (2000-2002), and on the Board of Directors of: the National Council of Teachers of Mathematics, the Benjamin Banneker Association, and the North Carolina Council of Teachers of Mathematics. He has been a member of: NASA's inaugural Education Advisory Committee; the Mathematical Sciences Education Board of the National Research Council; the NCTM Algebra Task Force; the Editorial Boards of the Journal for Research in Mathematics Education and Mathematics Teacher; the Instrument Development Panel for the 1994 NAEP Mathematics Assessment; and numerous national, regional, and state mathematics conference program committees.  

Dr. Stiff's research focus and other professional activities include effective teaching strategies, problem solving, the mathematics education of African-American children, and uses of instructional technologies in mathematics teaching. His research methodologies include experimental design, surveys and interviews, and classroom-based investigations. He has more than 100 publications, including the authorship, co-authorship, or editorship of twelve textbooks in middle grades and high school mathematics, six professional books and eight book chapters.