It is unknown how multiple components of on-task regulation of learning affect task performance in school children. This research aimed to acquire insights into the interrelations between children's metacognitive monitoring, regulation of learning, and task performance. Three components of on-task regulation of learning were investigated: allocation of study time, restudy selections, and task persistence. Children learned concepts with their definitions. In Study 1, 104 sixth graders (M[subscript] age 12 years) participated; Study 2 consisted of 97 fourth graders (M[subscript age] 10 years). For both age groups, task persistence was a strong predictor of performance. For sixth but not for fourth graders, monitoring accuracy affected performance. Findings indicate that, when aiming to improve regulation of learning and task performance in elementary school, student age is a relevant factor to consider. Around the age of 10, regulation affects learning performance, whereas the effects of self-monitoring accuracy on performance seem apparent when children are approximately 12 years of age.