Authors of computer-assisted learning (CAL) packages use graphs so that pupils can easily see trends in data generated by the program. Most authors do not realise that many pupils have inadequate graph interpretation skills and get very little information from the graphs. In order to interpret the displays successfully pupils need concepts relating to both the subject domain shown in the graph and the actual format of the graph. One of the most common problems which pupils face is interpreting questions which involve gradients. The paper discusses a pilot study which investigated four pupils working with an interactive computer program called SKETCH. This program has been developed to research into how pupils develop concepts of gradient through sketching and interpreting graphs. The program has been designed with a particular underlying pedagogy in mind, which is discussed in detail. SKETCH provides a very versatile environment in which pupils watch a dynamic screen simulation and then sketch a graph to represent that they have seen on a digitising tablet (bit pad). Then they can compare their sketch with the computers' graph. The SKETCH program enables pupils to move easily from one translation to another (i.e. simulation, graph sketching, graph interpreting). The program also has some special features which enable the researcher to log and play back pupils' performance data. The results of the pilot study indicate that the program is a rich learning environment for pupils and a valuable tool for the researcher.