The integration of web-based discussion tools in education has expanded rapidly, yet their pedagogical use remains largely unstructured, often resulting in fragmented discussions and limited learners' engagement. This gap reflects the absence of empirically grounded instructional models that align digital discourse with principles of collaborative knowledge construction. To address this challenge, this study introduces the 8Bs instructional model designed to enhance collaborative learning in web-based discussions. The model comprises eight interconnected stages: Browse, Brainstorm, Backchat, Balance, Bring, Backlog, Build, and Beyond. The development of this model was guided by a mixed-methods approach that combined qualitative data from theoretical analysis, feedback from students, teachers, and researchers. In addition, quantitative analysis of students' achievement tests, classroom observation, and validation of academic researchers were also taken into consideration. Subsequently, the model was validated through implementation in selected classrooms, with observations and feedback informing its refinement. Furthermore, the model underwent expert validation by specialists in chemistry education, curriculum studies, ICT in education, and educational planning from the University of Rwanda--College of Education (UR-CE). The validation results showed that the model is acceptable at 80.21%. Based on the evaluation dimensions, the results found that model valid at 80, 78.89, 81.11% in terms of theoretical alignment, practicability, and pedagogical aspects, respectively. It was found that each stage of 8Bs model plays a unique distinct role in fostering active engagement, critical thinking, and knowledge construction among participants, ultimately enriching the learning outcomes. Moreover, the study evaluates the effectiveness of model in regard to students' conceptual understanding, engagement, and teachers 'pedagogical effectiveness. In this context, the results showed that the performance of senior two (grade8) and senior five (grade 11) students increased from 53.24 to 68.67%, and from 47.42 to 70.63%, respectively, following the intervention. Teachers and students reported increased engagement, interaction, and active participation following the use of the 8Bs Instructional Model. They expressed appreciation for stages such as "Backchat" and "Balance," which encouraged peer dialogue and critical thinking. In terms of pedagogical practice, classroom observation results revealed significant improvements across all five domains after implementing the 8Bs Instructional Model. Mean scores increased from 53.5 to 74.5% in lesson design, 55.05 to 81.25% in propositional knowledge, 52.5% to 78.05% in procedural knowledge, 57.5 to 88.5% in communicative interactions, and 51.75 to 79.05% in student-teacher relationships. Therefore, this model emerges as a response to the evolution of digital education and acknowledges the need for structured methodologies that harness the potential of online collaboration and knowledge exchange.