Activation of prior knowledge is vital for reading comprehension. However, little is known about students’ perceptions of what prior knowledge they view as significant for improving their learning from textbook texts in civics. This study explores how Swedish ninth-grade students, aged 14–16, with diverse linguistic and educational backgrounds, engage with two grade-level civics textbook texts by drawing on their prior knowledge. A four-field model is used to closely study the possibilities with civics texts, focusing on students’ prior knowledge. Thematic content analysis of the students’ statements from two think-aloud sessions reveals the emergence of seven distinct categories of prior knowledge. For instance, parents’ narratives and teacher explanations are underlined as essential resources for students to enhance their comprehension of the content of civics texts, thereby supporting their civics learning. The findings suggest that challenges with civics texts may not be a result of a lack of prior knowledge but may rather be due to the limited opportunities the students receive to activate their prior knowledge when engaging with civics texts. The students report that they face challenges in activating their prior knowledge when they encounter language- and content-related difficulties with civics texts. This underscores the pivotal role of civics teachers in facilitating prior knowledge activation before, during, and after reading civics texts. The four-field model can be used as a tool for analyzing and understanding the intricacies of reading civics texts. Using the model could support civics teachers in designing instruction to minimize challenges and improve students’ learning in civics.