The aim of this study was to design, implement and evaluate a teaching sequence about plant nutrition for male Saudi students aged 15-16. Considering the Saudi context, conducting a study related to developing instructional materials is likely to be beneficial as the Ministry of Education is currently reforming science education, including developing new science textbooks. The choice to target plant nutrition was influenced by the significance of this topic in school biology and the widespread misunderstandings that students hold about it. A case study methodology employing a design research approach was used, involving four teachers and 131 students (from two schools). A design model was used to design the teaching sequence that brings together, using specific design tools, theoretical perspectives on learning and teaching, and empirical findings on students’ ideas about plant nutrition to inform specific decisions about teaching plant nutrition in the Saudi context. The resulting design was evaluated using an evaluation model that measures the match between what was intended from teachers and students and what they actually did, and what was expected from students in terms of learning and what they actually learnt. Data were collected using videos, written probes, interviews and classroom written work. Findings from the evaluation suggest that the sequence helped students to acquire factual knowledge relating to photosynthesis, as well as develop a conceptual understanding of the nature of plant food and the source of extra biomass. However, it was less effective with regard to promoting long-term retention of conceptual understanding. This limited effectiveness may be due to overlooking the relationships between photosynthesis and respiration, food and energy in the design, and providing a relatively limited focus on the construction and practice of scientific explanations. Based on evaluation results, some revisions were identified and a set of guidelines for teaching plant nutrition in Saudi schools was developed. Findings from interviews with teachers and students point out that both the teachers and students appreciated the sequence and associated pedagogic strategies, although these differed considerably from usual practice. Some general implications for designing and evaluating teaching sequences are proposed. In addition, specific implications for teaching scientific concepts in the Saudi context as part of a reform of science education are highlighted. Finally, suggestions for future research are identified.
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