Background: This study builds on posthumanist and new materialist orientations to examine the role of material properties and the gendered identity texts of educational tools as active agents in STEM learning. Methods: Over 200 youth, ages 5-15, were randomly assigned to 90-minute introductions to one of five commercial circuitry toolkits. Youth took a pre- and post-assessment; we analyzed results using quantitative tests of significance. We used an established sorting task to gather youth perspectives of the tools as identity texts through design markers of gendered identities within the toolkits. We examined the relationship between learning outcomes and the gendered design components of the toolkits. Findings: Toolkits that privilege feminine or artistic elements significantly impacted learning more than traditional toolkits used in schools, which showed little to no significant learning gains. We relate this to the inextricability of materiality and the gendered identities of these tools and materials. Contribution: This study shows how arts-based or feminine-coded tools can be more effective for teaching and learning, serving as a counter to common resistance to adopting such tools and materials for STEM learning. We outline design implications for toolkits and educational experiences to disrupt stagnant social, cultural, and historical norms in STEM education.