The aim of this paper is to contribute to the understanding of the possible influence of the use in class of Internet resources which offer mathematical exercises for the students' activity and learning processes. I present an exploratory study grounded on a teaching design set up in two French grade six classes about proportional reasoning involving an e-exercise resource. We adopted a teaching design which used free access for the student to a wide range of exercises, and many written reports associated with the work on the computer. We observe that the students' activity during the experiment is much richer than drill. Students develop different working patterns on the computer. These patterns can be interpreted as consequences of the different roles implicitly attributed by the student to the resource within the didactical contract. We also observe the construction of new mathematical abilities. At the end of the teaching, the students were able to use several kinds of strategies to solve proportionality problems. However the didactical contract is modified by the Internet resource and generates specific difficulties, in particular insufficient written work. (Contains 1 tables and 2 figures.)