This study quantified the possible learning losses in reading and math skills among a sample of Finnish Grade 3 children (n = 198) who spent 8 weeks in distance learning during the first wave of the COVID-19 pandemic in spring 2020. We compared their reading and math skill development trajectories across Grades 1, 2, and 4 to a pre-COVID sample (N = 378). We also examined if gender, parental education, maternal homework involvement, and child's task-avoidant behavior predict children's academic skills at Grade 4 differently in the pre-COVID sample compared with the COVID sample. Children's reading and math skills were tested, mothers reported their education and homework involvement, and teachers rated children's task-avoidant behavior. The results showed, on average, lower reading skills in the COVID sample than in the pre-COVID sample but there were no differences in math skills. Although the COVID sample had lower levels in reading, their developmental trajectories in reading and math skills were not different from the pre-COVID sample before the pandemic in Grades 1 and 2. From Grade 2 to 4, however, the development was slower in reading fluency and comprehension in the COVID sample, but not in math. The predictors of change from Grade 2 to 4 in reading and math skills were not different in the samples. The results showed that the development of reading skills in particular may have been affected by the COVID-19 pandemic.