The instructor and the interviewer were experts on PBL and clearly had full knowledge of the instructional method each participant received. This could be construed as a limitation of the study and would be important to consider in future studies.
The classes were originally comparable in terms of students labeled as “high need” (i.e., those reading below their grade level and those who spoke English as a second language).
Both classes were taught using an inclusion model, with 19 students being present in the comparison group and 21 students being present in the PBL experimental group.
The PBL experimental group included an autistic student as well as a student who had just enrolled prior to the beginning of the study and spoke
Journal of Elementary Science Education • Winter 2009 • 21(1) 11
only Arabic. In addition, absenteeism, as well as pull-out programs, resulted in some students missing a significant number of lessons (i.e., three or more). These students were unable to be included in the final results in some components of the study.