This research was to investigate the influence of the head teacher's instructional leadership practices on students' academic achievement in public lower secondary schools in Rwanda. Specifically, this study was to assess the influence of shared expectations on students' academic achievement in public day lower secondary school in Nyagatare District, Rwanda. Determine influences of resource utilization on students' academic achievement in public day lower secondary schools in Nyagatare, Rwanda, and determine the influence of supervision of instruction on student academic achievement in public day lower secondary schools in Nyagatare district, Rwanda. This study was significant to policymakers, head teachers, and the ministry of education. The study adopted a descriptive survey design. The targeted population in this study consisted of 7238 respondents. A total sample of 379 respondents from lower secondary schools in Nyagatare District, and the researcher used purposive sampling techniques to choose 3 headteachers and simple random sampling to choose 92 teachers and 284 students. The findings were analyzed through SPSS version 21, and interpretations were made based on results given by respondents. To the first objective, results indicate that 69.6% strongly agreed that headteachers share expectations with students and teachers; 80.4% strongly agreed that teachers and students are involved in developing expectations of their teaching and learning; 75.0% strongly agreed that shared expectations affect a student's resilience and ability; 66.3% strongly agreed that the headteacher communicates with teachers and learners on expectation of learning outcomes; and 59.8% strongly agreed that the headteacher engages in activities that sustain the school annual academic expectation. To the second objective, the study indicates that the results indicated that 79.3% strongly agreed that the availability and quality of resources, such as textbooks, technology, and learning materials, significantly impact students' academic performance. 80.4% strongly agreed that the headteacher is pro-active in harnessing resources to support instruction. 90.2% strongly agreed that the headteacher has developed a policy on the utilization of text books and other resources in our school, and 88.0% strongly agreed that the headteacher has implemented measures of effective teaching and learning resources. To the second objective, 72.8% strongly agreed that the headteacher carries out supervision during teaching and learning; 82.6% strongly agreed that the headteacher provides feedback after lesson observation. 72.8% strongly agreed that the head teacher checks professional documents like lesson plans, schemes of work, etc., and 64.1% strongly agreed that the headteacher delegates observations of lessons. For the students’ performance, the study indicates that 68.0% strongly agreed that increased students’ retention indicates their level of academic performance. 92.3% strongly agreed that students’ graduation rate indicates their level of learners’ academic performance, and 83.8% strongly agreed that improved examination and test marks indicate their level of academic performance. The study found a positive correlation between Head teachers' instructional leadership practices and students' academic achievement in Rwandan public day lower secondary schools, with Pearson's p-value and significance justified by p-values less than 0.05. The study recommends that to Invest in training principals to improve leadership skills, focus on instructional planning, foster a learning culture, regularly assess performance, collaborate with teachers, and involve parents in the educational process. Encourage clear plans aligned with learning objectives, foster a learning culture, and regularly assess student performance to adapt teaching methods. Involve parents in the educational process for reinforcement.