ABSTRACT:Researchers are becoming aware of the influence of students' presuppositions in directing their construction of science concepts. When these are entrenched and drastically nonscientific, they predispose the children to alternative explanatory frameworks that are inhibiting, especially in a knowledge domain such as genetics. In this study, we identified such nonscientific presuppositions among 17-to 18-year-old secondary school students from the Igbo community of Southeastern Nigeria. We designed a research-based instructional model to address these presuppositions. The relationship between the levels of nonscientific presuppositions held by students and their achievement in genetics was assessed. Finally, the effect of the instructional model on students' relinquishing these nonscientific presuppositions and on their achievement was determined relative to a comparison group. It was found that this group of students had nonscientific presuppositions that they used in explaining genetic phenomena, and that the present instructional model aided the students in relinquishing these nonscientific presuppositions to a great extent. We conclude that a conceptual change model that addresses explicitly nonscientific presuppositions will lead to an increased understanding of science concepts.

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This study set out to investigate the relationship between STS approach, scientific literacy (SL), and achievement in biology. A quasi-experimental design of the nonequivalent group was employed. Four secondary schools, eight teachers, and 246 students from Nigeria were involved in the study. Two classes were randomly selected from each school and assigned to either the experimental or control group. Two instruments were used to collect data: an Achievement Test on Reproduction and Family Planning and a SL Scale. Results showed that there is no relationship between SL and achievement in biology. The split-wise posttest regression showed a weak positive relationship between SL and achievement in biology for the experimental group and a no relationship for the control group. However, STS approach mediated between SL and achievement to effect a slightly stronger significant positive relationship. The slope of SL was greater when we controlled for instruction showing that the relationship between SL and achievement is not spurious when instruction is taken into account. We therefore conclude that STS approach might be affecting other variables in the science classroom that in turn affect achievement in the sciences.

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