Graphical literacy or graphicacy is a critical component of scientific literacy. Graphs are used to integrate and represent complex sets of information requiring abstraction from perceptual experience. They form essential parts of the Mathematics and Science curriculum across school curricular stages. A key to developing meaningful pedagogic practices to inculcate graphical literacy is in understanding how students perceive and comprehend features of graphs and interpret them. This study attempts to understand how children from the primary, middle and high school years, perceive and interpret information in bar and line graphs. Two hundred and twenty-nine children from four different school contexts in Grades 5, 7 and 9 were administered questionnaires and interviewed based on tasks requiring comprehension of graphs. It was found that children's understanding of graphs was tied to the curricular progression which was significant at Grades 5 and 9. Comprehension of bar graphs with nominal data was easier compared to line graphs requiring integration of information from two dimensions and interpreting them. Further, graphs requiring preliminary levels of statistical understanding were easier to comprehend. While prior experience and facility with graphical conventions played a role, interpretation from spatial to symbolic representations posed challenges. Students did not have a clearly preferred strategy or a linear comprehension trajectory, but moved back and forth between conventions, clustering of graphical elements and written content in questions, to make meaning. Those who had performed well used various perceptual strategies simultaneously. Further, they were found to employ transformational reasoning based on a sense of 'how things work'. It was observed that meaningful pedagogic practices at school and informal experiences outside the classroom aid graphical literacy.