The present study explored the issues related to subject combinations choice at advanced level secondary schools in Rwanda. Three schools with various subject combinations were conveniently selected from three districts in Rwanda. Two hundred and thirty-eight participants, including 211 students (grade 10 to 12), three director of studies (DOS), and 24 teachers, were selected purposively to participate in this study. A survey questionnaire for students, interviews with DOS, and focus group discussions with teachers were employed to collect qualitative and quantitative data for triangulation purposes. For instance, a questionnaire was used to reveal students' choice of their subject combinations, a DOS interview to learn how combinations are assigned to students, and teacher FGD to learn difficulties students face due to assigned subjects. Quantitative data were analyzed with descriptive statistics, while qualitative data were analyzed using thematic analysis methods. The results analysis revealed that some students studied what they chose, while others were given what to study based on their performance or influenced by their parents' preferences. Therefore, students reported that they struggled to perform successfully at A' level while they used to perform well at the O' level. It was noticed that what some students learn at A' level have a negative effect on their future life. This study recommends that (i) the career development stakeholders should sensitize students about the impact of the wrong choice, (ii) Rwanda Basic Education Board (REB) should train career guides to help students choose their best combinations, and (iii) students' interests should be given preference than their performance.