Building on the need for developing educational responses to the impact of data practices in our everyday lives, a new curriculum called Nayah-Irú was designed and implemented in the context of five alternative schools in Uruguay. Nayah-Irú aimed at fostering Critical Data Literacy (CDL) using speculative civic literacies, helping youth and educators envision possible futures for the use of data in their lives while challenging oppressive practices in digital platforms. By engaging in YPAR and Speculative Education, this curriculum aimed to facilitate the development of alternative perspectives to understand how data influences our lives while disrupting the normalization of datafication. The implementation of the curriculum involved artifact documentation and a youth research conference, followed by interviews with educators. This dissertation research explores how youth develop critical data literacy through the Nayah-Irú curriculum. It also examines how youth research projects serve as examples of civic participation and how educators facilitate the development of critical data literacy. Following the multiple-case study design, 7 interviews with educators and over 60 artifacts were analyzed that were collected over 12 weeks. The cross-case qualitative analysis revealed four overarching themes: (a) speculative storytelling and real-life experiences, (b) overcoming discursive loops through civic participation, (c) guided discovery as an approach to engage in CDL and (d) remapping challenges into opportunities. Based on these themes, the study proposes the Cartographies of Possibility framework to support CDL through a place-based approach that intersects speculative play and YPAR, aiming to overcome discursive closures in relationships with data. The research holds significance for educators, researchers, and stakeholders interested in fostering critical data literacy among youth from a sociocultural perspective, positioning data literacy as a liberatory practice that cultivates awareness of systemic injustices and inspires youth to imagine more equitable futures.