Is developing scientific thinking all about learning to control variables?

Academically low-performing urban sixth graders engaged in inquiry activity received a suggestion that they focus their investigation on the role of a single factor. This suggestion had significant effects on their use of a superficially dissimilar strategy--controlling the variation of other factors. This latter strategy has received the lion's share of attention in research on the development of scientific reasoning. These results have implications, we propose, for what undergoes development with respect to scientific thinking and how this development can best be facilitated.