Social technologies are leading to transformations in education, by empowering the way learners connect to each other, by introducing new means for teaching and learning and by reshaping the way knowledge is delivered. Annotating texts is a learning strategy that is spontaneously adopted by learners during lectures or while reading text books. Students still individually take annotations on paper, that tend to be thrown away when the learning goal is achieved. Students also engage occasionally in the spontaneous practice of note sharing. Our work explores experimentally the benefits of note-taking and note-sharing behaviour. First, we study how sharing student-annotated instructional texts can improve learning, enriching an experimental approach with a new eye tracking method. Second, we conduct experiments on computer-mediated note sharing in the classroom. Our results demonstrate the virtuous circle of note-taking: both annotating while reading and reading annotated documents lead to a better learning achievement. In the first experimental study, we measure if the presence of annotations, on an instruc- tional text, can influence the reading pattern, and how visual features of annotations can elicit the reader’s attention. To complement the results concerning learning and reading comprehension, we look into the readers’ gaze patterns, to explain how the students’ learning outcome relates to reading annotated texts. For this purpose, we design a novel eye tracker, that can be used to study reading and note taking in unconstrained experimental settings. This eye tracking system is based on a systematic error correction procedure that exploits the appearance similarity between the annotated texts and the spatial distribution of the fixation points. We show that this method can extract accurate gaze measures without introducing experimental constraints, that could disturb the note taking process and affect the readers’ comprehension. In the second study, we move from a controlled experimental setting to the classroom. We discuss how the use of technology can facilitate a spontaneous transition from personal to shared annotations and support students in the learning process. We complement the analysis by reporting a friendship bias in browsing the shared annotated material. We further speculate on the potential of shared annotations in triggering adaptations of the instructional material and teaching workflow. These two studies provided an insightful understanding of the effects of student-generated annotations on reading comprehension, and the underlying impact on a community of learners. The obtained findings should inspire further experimentation on social learning environments, meant to facilitate knowledge sharing through shared annotations and their diffusion within educational institutions.