The present study examined the influence of teachers’ presence skill and students’ grade on learning performance across 15 weeks in a whole semester. Data were collected from 148 online extra-curricular English courses for more than 200,000 Chinese primary students. Teachers’ presence skill was evaluated by experts familiar with K-12 online education. Using Hierarchical Linear Modelling (HLM) analyses, the results suggested that students taught by teachers of high presence skills achieved higher scores than those taught by teachers lacking such skills. Besides, high-grade students remained stable performance across the semester. However, the performance of middle-grade students tended to drop quickly after some critical milestone (e.g., the first class and the mid-term examination) but improved quickly before examinations. The different patterns may be attributed to the differences in students’ self-control abilities and time allocation strategies between online and offline courses. The findings were beneficial to human-computer interaction (HCI) researchers and practitioners who develop new methods to improve teachers’ presence skill and also important to design more age-adaptive courses.