Further to Steve Alessi's comments on a systems modeling tool, I would like to add that there is a London Mental Models Group in the UK (centered on London universities) that has conducted extensive research (over 1989-1992) on the use of various modeling tools, including, to encourage learning in children of various ages (but particularly, high school, ages 14-18). This group has since diversified, to include French and Danish researchers, under the ESPRIT (EEC) initiative.
The group has also designed a range of modeling tools, some based on knowledge based systems (essentially for building "qualitative" models) and some based on a mix of quantitative and qualitative approaches to representing knowledge. Although there are many publications from their work, one book provides a good survey of developments (Mellar, H., Bliss, J., Boohan, R., Ogborn, J., & Tompsett, C. (Eds.). (1994). Learning with artificial worlds: Computer based modelling in the curriculum. London: Falmer Press). One can also locate a number of their more pivotal publications in the Journal of Computer Assisted Learning.