Since 2022 Member of the Board of Trustees of the Hamburg Scientific Foundation
Since 2019: President of ICTMA - The International Community of Teachers of Mathematical Modelling and Applications
Since 2017: ICMI-representative for Germany
Since 2009: Member of European Association for Learning and Instruction (EARLI)
Since 2007: Member of the German Mathematical Society (Deutsche Mathematiker-Vereinigung (DMV))
Since 2005: Member of the German Association for the Promotion of Mathematics and Science at School (Deutscher Verein zur Förderung des mathematischen und naturwissenschaftlichen Unterrichts (MNU))
Since 2001: Member of the "International Group for the Psychology of Mathematics Education" (IGPME)
2007-2011: President of ICTMA - The International Community of Teachers of Mathematical Modelling and Applications
1988-1991, since 2006: Member of the Advisory Board of the Society of Didactics of Mathematics (Gesellschaft für Didaktik der Mathematik (GDM))
2002-2004: Member of the Advisory Board of the Journal Mathematik-Didaktik (Mathematics Didactics)
2000-2002: Secretary of the Society of Didactics of Mathematics (Gesellschaft für Didaktik der Mathematik (GDM))
2000-2005: Member of Advisory Board von Swedish National Mathematics and Science Tests (SweMaS)
Since 1999: Member of the German Society for Education (Deutsche Gesellschaft für Erziehungswissenschaft)
Since 1999 and Applications (ICTMA)
Since 1998-dato: Initiator and leader of the working group "Empirical Research in Mathematics Teaching" ( before named "Comparative Research in Mathematics Teaching") of the Society of Didactics of Mathematics (Gesellschaft für Didaktik der Mathematik (GDM))
Since 1991: Member of ISTRON Group on the teaching an learning of mathematical modelling
1989: Founder – together with Cornelia Niederdrenk-Felgner – of the working group "Women and Mathematics" of the German Society of Mathematics Education (Gesellschaft für Didaktik der Mathematik (GDM)), Leader of the working group until September 1996, and again from 2004 until 2006.
Since 1981: Member of the Society of Didactics of Mathematics (Gesellschaft für Didaktik der Mathematik (GDM))