"The Imagineerium" is an arts and engineering based curriculum project designed to enhance student confidence in learning. This study reports on the development of the Trowsdale Index of Confidence in Experiential Learning, an instrument designed to conceptualise and operationalise a four-component model of confidence in experiential learning appropriate for upper primary school students, embracing confidence in creativity, confidence in competence, confidence in collaboration, and confidence in learning. Data provided by 140 9- to 10-year-old students both before and after participating in the 10-week programme, demonstrated a significant increase in scores on this measure at time two, although there was no increase in scores on a control variable hypothesised not to be influenced by the intervention.