The vast majority of American students are neither prepared nor sufficiently engaged to become science, technology, engineering, and mathematics (STEM)-literate citizens or innovative STEM professionals (National Research Council, 2007; Carnegie Corporation and the Institute for Advanced Study, 2009; National Science Board [NSB], 2010; President's Council of Advisors on Science and Technology [PCAST], 2010). The Citizen Schools Expanded Learning Time (ELT) model is defined by two core components: Apprenticeships and Academic Support, both of which are built into a lengthened school day. The Apprenticeships are the cornerstone of the Citizen Schools ELT program model; they are designed to engage student interest in a broad array of subject areas and experiences by leveraging expertise and commitment from local communities. Over the past several years, Citizen Schools has endeavored to increase both the number and range of STEM-focused apprenticeships, responding to increased demand and recognizing the importance of engaging middle school students in STEM subjects through a combination of hands-on learning and exposure to enthusiastic ambassadors for professional careers in STEM fields. This study examines whether the STEM-focused apprenticeships, in particular, serve to engage students in STEM learning, and increase their interest in STEM subjects more so than apprenticeships in other topics. [The report was prepared for Citizen Schools.]