Augmented Reality (AR) is an emerging technology with measurable benefits for students and teachers. However, it is sometimes difficult to use, especially for young-aged users, which may negatively affect learning experience. Many researchers agree that to achieve the technology’s unique benefits, AR designs should take into consideration students’ abilities and limitations that derive from their physical and cognitive development. In the case of primary school students (aged 6-12), the need for appropriately designed AR experiences is higher, as children’s abilities are still developing at this period of their lives. The present research aims to understand how children’s level of motor and spatial abilities relate to the use of certain interaction types of mobile AR. Students’ cognitive scores will be correlated with usability metrics and performance data, while using four different interaction types in a specially designed mobile AR game application. The results may lead to the formation of a set of guidelines for designing usable mobile AR applications that comply with primary students’ cognitive development.