Children possess different beliefs regarding their ability to succeed in math and science, as well as different levels of enjoyment and interest in these topics. These motivational processes are important because they often shape learning-related behaviours which in turn predict academic outcomes, over and above previous performance. But, what are the potential sources of influence that could explain individual differences in children's academic self-concept and interest in math and science? In this registered report, we adopted a situated expectancy-value theory framework to examine the potential role of teacher instructional practices that emphasize conceptual understanding in enhancing these motivational processes. We focused on practices emphasizing conceptual understanding given science-driven recommendations to implement them across the United States. Contrary to our hypotheses, a multilevel analysis of grade 4 U.S. data from the 2015 release of the Trends in International Mathematics and Science Study (TIMSS) revealed that the self-reported frequency of instructional practices emphasizing conceptual understanding were unrelated to math or science self-concept and interest. Our null findings prompt greater attention to other factors, such as the quality and implementation of instructional practices, differences between instructional goals and actual practices, and classroom composition, that could enhance ability beliefs and values in math and science.