The underconfidence with practice effect (UWP) refers to the finding that people's judgments of learning shift from overconfidence to underconfidence on and after a first study-test trial (Koriat, Ma'ayan, & Sheffer, 2002). Finn and Metcalfe (2007, 2008) proposed that people show UWP because they use their memory of prior test performance as a cue to make subsequent judgments of learning and inadequately account for new learning (i.e. the Memory for Past Test (MPT) heuristic). In contrast to adults, 3rd and 5th graders' judgments showed persistent overconfidence on and after a first study-test trial. A second experiment tested children's ability to remember their prior test performance. Children's prior performance discriminations were accurate for items that they answered correctly on the prior trial, but were overconfident for items they had answered incorrectly indicating that their continued overconfidence was a result of faulty memory, rather than a failure to use the MPT heuristic.