This project addresses the need to provide students with better mechanisms within digital libraries, such as the National Science Digital Library (NSDL), to find information. Prior research in the design and cognition of hypertext systems points to the use of graphical aids to help navigation and learning; and educational psychology research shows the value of concept maps to support learning of rich relationships between science phenomena and principles. The project, therefore, is using conceptual linking in the form of concept maps to enable students to explore questions and follow their own paths. To achieve this aim, the CoMPASS-DL system is being developed with an interface that provides navigable concept maps that helps students to select resources based on the relatedness of the documents to each other as well as to students' goals. CoMPASS-DL is being used in middle schools in Wisconsin to understand the impact of digital libraries in classroom learning. The project also enables NSDL community members who are designing resources for K-12 students to better understand how digital resources can be integrated in inquiry-based science classes.