Despite the popularity of task-based language teaching (TBLT) in foreign language (FL) education at elementary school, it remains unclear how young learners' FL abilities can best be evaluated with tasks. The present study seeks to understand developmental differences in interactions among elementary-school students during task-based language assessment (TBLA) and aims to address the possibilities and limitations of introducing paired-TBLA among young FL learners. The participants were 32 fourth-grade students (ages 9-10) and 32 sixth-grade students (ages 11-12) and their teachers from a FL program where TBLT was mandated. The students were engaged in two sets of assessment tasks with their peers. It was found that the interaction patterns were different between the two grade levels. Compared with the sixth-grade dyads, the fourth-grade dyads showed less mutual topic development, used formulaic turn-taking more frequently, and had a harder time taking their partners' perspectives during the tasks. Consequently, a smaller variety of interactional functions were observed among the fourth graders. The potential for eliciting a wide range of interactional functions, which is a primary advantage of introducing paired assessment, may have limited application for younger dyads. The study also discusses the strategic roles that such interactional characteristics may play among younger learners.