The aim of this research was comparing the performance of primary school Chilean children when reading different types of graphs included in the primary school curriculum in this country (pictogram, line graph, pie chart and dot plot). A sample of 745 6 th and 7 th Grade students were given a questionnaire including four tasks in each of which they should perform a critical reading of one of these graphs. The analysis of the children written responses to the questionnaire served to compare the tasks difficulty when measured by the percentage of correct responses and to study the reading level achieved in the children's responses using the classification of Curcio and his collaborators. Globally, the children obtained 60% or more correct responses except when reading the pie chart that was the most difficult task, probably because of the need of proportional reasoning, which is still developing at this age. Few children succeeded in attaining the critical reading level N4 in their responses, although most of them achieved the reading level N2, which implies not only a literal reading, but also the ability to compare the data or perform computations with the same.