To explore the ways in which teacher-guided and student-centered instructional approaches influence students' conceptual understanding of seasonal change, we designed a technology-enhanced learning (TEL) course to compare, by means of concept maps, the learning outcome of students in two groups: a teacher-guided (TG) class (with whole-class presentations) and a student-centered (SC) class (with individual online learning). The participants were two classes of second-year senior high school students in Taiwan. Overall, the results showed that most students developed a deep and accessible understanding of the reasons for the seasons after undergoing experiences provided by the TEL course. More importantly, it was found that, in this technologically enhanced environment, the student-centered approach was more effective than the teacher-guided approach in altering students' alternative conceptions of seasonal change (F = 28.05, p less than 0.001). The conceptual evolution of students in the two groups was plotted and compared. These plots indicated that, first of all, the cognitive processes of contextualization and sense making helped students re-examine their old ideas about the phenomena, leading them to generate alternative conceptions and undergo both positive and negative conceptual change. The student-centered approach allows students to more freely test their own hypotheses in the processes of exploration and modeling, and thus move from assimilatory to properly scientific explanations. (Contains 5 tables and 7 figures.)