The use of texts is an indispensable resource for students' learning, especially in science domains. While developing understanding of a specific topic usually is the main goal of reading expository texts, an important consideration is how to best measure whether this understanding has been reached. In this study, we aimed to analyze gains in students' reading comprehension based on reading three expository texts on chemistry and physics topics. By means of a pre-post design, we assessed the reading comprehension of 261 eighth grade students with regard to three levels of reading comprehension. Latent change scores were estimated to analyze changes in students' total test scores, while also calculating difference scores based on the single items. Results indicate that students' topic-related comprehension increases from pre- to posttest, while gains seem to be limited to word and sentence level questions. In line with other studies, these findings stress that students would benefit from explicit strategy instruction, at least when learning from reading is the goal of using science texts in classrooms.