Guided and open inquiry stands as a valuable instructional strategy for science education. Yet, confirmation and structured inquiry, which provides higher levels of teacher guidance, is more often enacted. These approaches, though more workable, remain unexplored in their effectiveness in improving achievement motivations. This study draws on expectancy-value theory to explore the effect of short-term confirmation and structured inquiry on students' expectancies of success and intrinsic values in school science when compared to traditional lecture-based strategies. One hundred and nineteen Spanish sixth graders were assigned to three pedagogical conditions using classroom clusters: lecture (control group), confirmation inquiry, and structured inquiry. The intervention consisted of two units of three hours each. Findings revealed no statistically significant differences between pedagogical conditions. Overall, this study failed to find evidence of a difference in students' expectancies of success and intrinsic value of school science when lecture, confirmation, or structured inquiry teaching strategies were used.