the moon phases, the systematicity of their observations, and their ability to draw valid conclusions (e.g., to identify successive phases, the periodicity, and the period of the phenomenon). Then, a set of sixty-one cards was presented to the students. Each card showed the date and a photograph of the moon as it appeared on the sky for each day of October and November. The students were asked to organise the set of cards and draw as many conclusions as possible. Students, who failed this task, were then asked to draw conclusions from a set organised data (cards showing successive phases of the moon) taken from a moon calendar. Finally, four cards were successively presented to the children, each one showing a phase of the moon (first quarter, full moon, third quarter, and new moon), and the students were asked to predict, in each case, the shape (phase) of the moon five days prior to or after the phase presented on the card. Students' behaviors made it possible to identify qualitatively different stages of development in terms of observational, classification, conclusion-drawing and prediction skills. The results showed that for the age range of 8-11 years, these skills develop gradually, but full development is not achieved. Several students also failed to develop conservation and mental rotation skills that seem to be directly related to the science process skills examined by the study. The results indicate that instruction at the primary school falls short in developing science process skills that constitute basic learning objectives. Recommendations for further research and for the design and implementation of inquiry-based learning environments conducive to the development of science process skills are presented.
Key words: phases of the moon, science process skills, prediction.