Evidence of the effects of indiscipline on the academic performance of grade 12 learners has been mixed. This study examined how indiscipline in the forms of disruptive, aggressive behaviour, alcohol and drug abuse affected levels of academic performance in a case study of public Senior Secondary Schools of the Libode Education District, Eastern Cape Province in the Republic of South Africa. A total of 25 teachers from two selected schools in the Libode District (10 men and 15 women) were randomly assigned to participate in both the quantitative and qualitative interview surveys conducted by the researcher. The study relied substantially on teacher ratings. The data were collected using interviews which were synthesized, analysed, presented and discussed within a specified time frame. The results adequately reflected on the three research questions of the study which were: To what extent do learners‘ aggressive and violent behaviour impede academic performance? Does imbibing alcohol and drugs influence learners‘ academic performance? To what extent does learners‘ disruptive behaviour affect their academic performance? It has been clearly indicated that disruptive, aggressive behaviour and alcohol and drug abuse have a negative impact on academic performance. The factors (disruptive, aggressive behaviour, alcohol and drug abuse) used in the analysis were identified as the main challenges to the educational development and academic achievement among learners; they pose a serious threat and have negative effects on students, teachers, the school environment and society. They originate from the same sources, however; these are mainly family background, society, cultural values, beliefs, technology, peer pressure and classroom management strategies employed by educators. Findings were discussed in the context of the main and sub research questions and recommendations were made.