When compared to high performers, low performers generally have more difficulty to accurately estimate their own performance. This has been explained by low performers being both unskilled and unaware about their performance. However, Miller and Geraci Journal of Experimental Psychology: Learning, Memory, and Cognition, 37(2), 502-506, (2011) found that low performing university students also assigned less confidence to their estimates (i.e., second-order judgments, SOJs), indicating some metacognitive awareness of their poor calibration. The current study examined whether the relationship between calibration accuracy and confidence in performance estimates is more general, and exists irrespective of performance level, not only for university students but also for secondary school students. We asked university students and secondary school students to estimate their exam grade after taking their exam, and to provide a second-order judgement). The results showed that for university students, poor calibration accuracy was indeed accompanied by low confidence scores, independent from performance level. For secondary school students however, calibration accuracy was unrelated to confidence scores, suggesting a less developed metacognitive awareness.