This paper examined the nuances of the background process of design and development and follow up classroom implementation of computer-based models for high school chemistry. More specifically, the study examined the knowledge contributions of an interdisciplinary team of experts; points of tensions, negotiations and non-negotiable aspects of model design; and the evolutionary trajectory of technological artefacts as they are readied for classroom implementation. A Discourse-in-use methodological approach examined planning sessions involved in the design and development of models and a case study of classroom implementation in two high school chemistry classrooms were conducted. The data included transcripts of planning sessions, classroom observations and teacher and student interviews. Design and development sessions reflected five major themes: (i) the nature of models: function, goals and limitations of models (ii) the role of students, background knowledge, and goals for student learning (ii) pedagogical decisions of the modeling process (iv) models and assessment and (v) the role of implementation. In comparison to the educator group, the scientist/programmer knowledge contributions dominated the form that technologies eventually assumed. Surely, implementation exposed teacher and student challenges with sub micro NetLogo representations; this finding reinforced the tensions and non-negotiable aspects of design that were involved in ensuring accurate representations. Models were configured to accommodate what was scientifically and technically reproducible within the constraints of context. However, these visual representations were not always commensurable with chemistry expectations at the high school level. These findings have implications for pedagogical decisions aligned with implementation, content understanding and assessment; and the sustainability of computer-based models in precollege science classrooms.