Humans tend to avoid cognitive effort. Whereas evidence of this abounds in adults, little is known about its emergence and development in childhood. The few existing studies in children use different experimental paradigms and report contradictory developmental patterns. We examined effort-related decision-making in a sample of 79 five- to 11-year-olds using a parametric induction of cognitive effort and three paradigms that each involved decision-making between low- and high-effort options but varied in how explicit effort was made. This included a demand avoidance and an effort discounting paradigm. We also probed cognitive processes linked to effort-related decisions, including task performance, metacognitive accuracy, effort perception, and mental demand. We found that children of all ages were sensitive to parametric modulations of cognitive effort as indicated by self-report. In terms of effort-related decision-making we found that overall children demonstrated no implicit behavioral preference for low effort tasks, that older children stated a preference for low effort tasks, and that all children discounted effort. Further, implicit preference in the demand avoidance paradigm was linked to children's metacognitive insight into how well they could perform effortful tasks. These findings strongly suggest that although children are clearly sensitive to manipulations of cognitive effort, whether and when they use this information to guide their decisions to engage in effortful tasks depends strongly on the extent to which effortful features are made salient to them.