Engineering education for sustainable design often focuses on technical solutions with little consideration of social impact. This paper presents a case study of a project-based learning (PBL) studio course engaging engineering students in social and sustainable design practices with external clients in developing economies. The case is a review of how concepts from Socially Responsible Design (SRD), Appropriate Technology (AT) and Human-Centred Design (HCD) integrated into a pedagogical model (Locale) focusing student effort on the socio-cultural, technical, economic and environmental aspects. Drawing on data from ten years of course operation the analysis identifies three distinct variants. Re-examining all 186 design projects using a new metric based on the pedagogical model (Locale) revealed an upward trend in the socio-cultural and economic appropriateness of the solutions without any diminution of technical suitability. Thus, the paper provides a new approach for designing and evaluating PBL courses specifically focused on social and sustainable design.