Digital technologies are part of many children's everyday lives. They use them for entertainment, information seeking and connecting with friends on social media. These shifts in children's literacy practices have impacted the ways in which they learn. As more children are engaged with digital technologies, critical literacy practices are vital, particularly in our current "fake news" and misinformation era. This paper describes a case study that examined a class of elementary grade students' engagement with critical literacy practices during their problem-based learning (PBL) projects in science classrooms. A group of English language learners (ELLs) in this classroom have attracted our attention throughout our study, particularly the unique ways they engage with critical literacy practices. Our findings suggest that students are using their critical literacy skills for evaluating the validity of online information and sources during their problem-based learning projects. We conclude with suggestions to support elementary science teachers who are interested in integrating critical literacy practices within a problem-based learning approach.