An issue that needs to be addressed is the ecological validity of the study. The experiment was integrated into an existing curriculum, and the experimental sessions took place
in the school during regular school time. On the one hand, this arrangement helps to
guarantee the ecological validity of the study and its results; but on the other hand, it
makes it hard to maintain strict experimental rigor during the experiment. For example,
in the school setting, it is impossible to keep participants from both conditions isolated
from each other for nine weeks. Of course, the participants were in two separate computer
classrooms during the experimental sessions, one room for each condition, but the participants could not be kept separated during the other school hours. The possibility that participants mixed, which could muddy the effects, cannot be ruled out. Yet, for two reasons
we believe that it is unlikely that this actually happened. First, outside the classrooms
(e.g., during breaks), these students talk about a lot of things, but hardly about subject
matter treated in the classrooms. Second, one would suppose that muddying the effects
because of mixing would lead to more equal posttest scores for both conditions. Therefore, if muddying occurred in our study, then the observed effects actually underestimate
the true effects. Being an underestimate or not, the ecological validity helps to establish
the value of inquiry learning within a virtual lab by showing that the beneficial effects can
actually be observed in the daily practice of the school.