Parental knowledge is often the result of parents soliciting information from their child and their child's disclosure of that information. Although child disclosure is most closely (and negatively) associated with behavior problems in adolescence, it is not yet known whether this is also the case in childhood. The aim of this study was to examine the longitudinal associations between child disclosure, parental solicitation, and behavior problems in Grades 1 to 4 in a Canadian sample, taking into account intra-individual stability, the child's gender, and socioeconomic status. The mothers and teachers of 911 children (62.7% boys) completed questionnaires in Grades 1, 2, 3, and 4. A Random Intercept Cross-Lagged Panel Model (RI-CLPM) showed that behavior problems in Grade 2 predicted an increase in parental solicitation in Grade 3. In contrast, behavior problems in Grade 3 predicted a decrease in parental solicitation in Grade 4. No cross-lagged association with child disclosure was observed. Although these results differ from those reported in adolescence, they suggest that middle childhood is a sensitive period for parent-child communication and behavior problems.