This concluded grant (2014-2016, $20,000, PI Jacobson) was funded by the Proffitt Internal Grant Program at Indiana University. The major activities carried out during the grant period included (1) developing a psychometric instrument for measuring preservice elementary teachers’ knowledge and beliefs for teaching multidigit subtraction, (2) designing an interactive online environment for authoring storyboard explanations and to facilitate learning to use concrete materials to support explanations, (3) a descriptive interview study of preservice teachers learning during their methods class, and (4) an experimental study of an intervention that used the online authoring tool and included outcome data from the psychometric instrument.