During category learning, students struggle to create an optimal study order: They often study one category at a time (i.e., blocked practice) instead of alternating between different categories (i.e., interleaved practice). Several interventions to improve self-study of categorical learning have been proposed, but these interventions have only been tested in learning tasks where students "did not" create the study order themselves. Instead, they decided which type of study order to follow. This pre-registered experiment examined whether an intervention that combines refutations and metacognitive prompts can enhance students' engagement in interleaved practice, specifically when they organize the learning materials themselves. Ninety-one undergraduate students were randomized into the intervention and control condition and learned visual categories. Prior to the intervention, students used more blocked practice. After the intervention, the use of interleaved practice significantly increased in both immediate and delayed-transfer tasks. More interleaved practice was associated with better classification performance. Our findings indicate that refutations and metacognitive prompts form a strong intervention that corrects students' erroneous beliefs and increases their engagement in interleaved practice.