- Professor of Mathematics, Department of Mathematics, University of Massachusetts, Dartmouth, MA, USA. August 2004-present.
- Chair, Department of Mathematics, July 2006- April 2008.
- Director, Office of Undergraduate Research, 2011-2013.
- Boeing Distinguished Professor of Mathematics Education, Department of Teaching and Learning, College of Education, Washington State University, Pullman, Washington, USA, August 2002 – July, 2004.
- Professor, Department of Teaching and Learning, Graduate School of Education, Rutgers, The State University of New Jersey, USA, August 2001-June 2002.
- Visiting Professor, Mathematics Education Research Centre, Institute of Education, University of Warwick, Coventry, UK, January 2001-July 2001.
- Professor, Research and Graduate School of Education, University of Southampton, United Kingdom, December 1995-2000.
- Reader, Department of Mathematics, LaTrobe University, Australia, 1992 – 1995
- Director, Institute of Mathematics Education, LaTrobe University, Australia, 1991 – 1995