A glance at any newspaper shows that graphs play an important part in presenting data to the public. It appears self-evident that children need to develop "graphical literacy" as part of their mathematics education. As part of a series of mathematically orientated science activities in the Practical Mechanics in Primary Mathematics project, 102 upper primary children measured the distance traveled by a falling ball for different time intervals, presented their data in a bar graph and commented on what they thought was happening to the speed of the ball. Children's graphs and written comments were analyzed from two perspectives: the degree to which the graphs conformed to graphical conventions (including their accuracy in representing the data), and what children inferred about the motion of the ball from their graphs. Results of the first analysis show that the majority of children understood bar graph conventions, while the second analysis reveals that the children's "graphical literacy" is at various stages of development. (Contains 15 references.) (Author/SAH)