Clarifying the relationship between science teachers' pedagogical content knowledge and student learning outcomes

Abstract

Pedagogical content knowledge (PCK) is the content-specific teacher knowledge that effective teachers use for promoting student learning of specific subject matter. Although PCK is often intuitively assumed to be crucial for promoting student learning, the few empirical studies examining the relationship between science teachers’ PCK and student learning outcomes have so far produced mixed and even conflicting findings. This study provides robust empirical evidence that clarifies the relationship between science teachers’ PCK and student learning through three interrelated sub-studies. Distinct from prior studies, this study adopted two approaches (text-based vs. video-based tests) to assess if, and to what extent, teachers’ two forms of PCK (the more static and declarative vs. the more dynamic and situated PCK) are related to student achievement. Study One developed and validated two novel video-based PCK instruments for assessing the more situated and dynamic form of PCK that informs teachers’ decision-making, approximated in the video-based tests for two biology topics. Results from the Rasch modeling analysis obtained from 261 Chinese middle-school biology teachers provided evidence that the instruments have acceptable psychometric properties. Study Two used a mixed-methods design to compare the two types of PCK test. Of the 261 teachers in Study One, 147 teachers’ test scores and test reactions in the video-based PCK test were compared with those of the same teachers in the text-based PCK test. A subgroup of teachers (N = 30) with different levels of PCK was interviewed to further understand their reactions to the test and how these might have affected their test performance. The results showed that teachers’ PCK scores in the video-based test were related to the text-based scores but were significantly lower. In terms of teacher reactions, teachers felt more authentic, job-related, immersed, engaged, and putting more effort, but experienced greater cognitive demand and anxiety, in the video-based test. A multiple regression analysis revealed that the cognitive demand perceived by the teachers significantly predicted their PCK scores in the video-based test. Study Three investigated the relationship between 147 Grade 7 teachers and their students’ learning in two topics (photosynthesis: N = 5,530; ecosystem: N = 5,622) by hierarchical linear modeling analysis. The results revealed a significant, positive association between levels of the two forms of PCK and student achievement. Significantly, the more situated and dynamic form of PCK assessed by the video-based test predicted student achievement better than the more declarative and static form of PCK assessed by the text-based test. Taken together, the findings of these studies reveal that both science teachers’ performance and test reactions are different in the two types of PCK test, and provide much-needed evidence to support the basic premise of PCK research that teachers’ PCK is related to student learning. These findings are essential for establishing the value of PCK as a viable construct for investigating science teachers’ professional knowledge. Implications for standardized PCK assessment, research on science teacher knowledge and science teachers’ teaching and learning as well as policy implications for assessment of teacher quality and teacher professional development, are discussed.