Background: Practical work is widely seen as a necessary part of a good physics education, but convincing evidence that it impacts positively on pupils' learning is scarce. Recent work suggests the use of talk and discussion might hold the key to making practical work more educationally productive. Purpose: The research question that this study aims to answer is: "Can the use of targeted discussion improve learning through practical work?" Sample: The study took place in a medium-sized (700-pupil, Years 7-13 (ages 11-18)) mixed-gender independent (fee-paying) day school in southern England. It is academically selective and public examination results are above the national average. The activities were carried out with three teaching groups (n = 73) with a fourth being used occasionally for comparison purposes (giving n = 97). Design and methods: Pupils were given a number of practical tasks--some from the usual scheme of work, some devised for this project--and given specific time to discuss with a partner the various aspects of the practical such as predictions, devising methods, problem-solving, conclusions or explanations of phenomena. Questionnaires and booklets were used to gather pupil responses. Some audio recording and analysis of pupil-pupil discussion was also done. Results: There was evidence from booklets pupils filled in during the practical that prescribing the use of discussion at various points in a practical task led to improved outcomes, particularly on the more cognitively challenging tasks. In particular, discussion was seen to turn incorrect responses into correct ones much more frequently than the reverse. In a later exam, pupils who had participated in the discussion activities performed better than a control group on questions which directly related to practical concepts, but performed similarly on the remaining exam questions. Conclusion: Evidence gathered suggests a more nuanced pattern than that reflected in previous literature: that discussion during practical work can impact positively on pupils' understanding of ideas related to practical work, but does not necessarily have a positive impact on their wider understanding.