Spatial skill assessment and training are promising fields of application for tablets, as touch-based interaction can prime and support mental transformations of spatial knowledge. We report on a study with 49 secondary school students who used our iPad app to solve mental and physical rotation tasks. During physical rotation, students were able to rotate 3D stimuli using touch interaction. Results show specific similarities (e.g., regarding angular disparity effects) as well as differences between mental and physical conditions, such as for task success, mental effort, efficiency; all to the advantage of the physical condition. 12-13-year olds can benefit from these advantages without previous task training, whereas previous research showed this to be different for younger students. In a second step, our analysis compares low and high achievers regarding physical rotation behaviour and motivational variables, including expected success. The results lay grounds for constructing individualized, tablet-based training apps for spatial skills.