Despite the almost mandatory inclusion of a laboratory component in the school curriculum very little has been reported about the effects of laboratory instruction upon student learning and attitudes. The present study was undertaken to investigate the thinking of students in a chemistry laboratory. An interpretive research method was adopted in collecting and analysing data gathered from observations, general interviews and stimulated recall interviews. Four high school students were studied during their participation in a week-long university summer school program. This study reports how the four students responded differently to the same laboratory experience.