In recent years, it has become common to use the internet or computer tutoring with a programme or application for additional instruction (ICTPAAI), in addition to the mandatory school schedule. This study aimed to understand students' participation in ICTPAAI and its relation to academic achievement. Multilevel structural equation modelling was conducted on a sample comprising 6,425 Chinese students (M[subscript age] 15.72 years; 48.9% girls) who had various forms of additional instruction during the 2014/2015 school year. Results showed that the use of information and communication technology (ICT) to complete schoolwork, whether in school or outside of school, was positively associated with students' participation in ICTPAAI; however, students' ICT interest, ICT self-efficacy and ICT autonomy were not. Students' participation in ICTPAAI was negatively associated with their academic achievement at the end of the school year; much variance was explained at the school level. These findings suggest that students should be cautious about participating in this form of additional instruction and that schools play an important role in students' participation in ICTPAAI.