The interior spaces of educational buildings can be considered as small environments for learning, gaining culture, having fun and social interacting with people. Students spend most of their time in these spaces and they are affected by the elements of the interior design. Assessment of the quality of the educational interior spaces is an important step which should be conducted to develop this type of spaces to be more sustainable in terms of environmental, economic, and social aspects. Therefore assessment should be conducted precisely and objectively and it should not depend on the opinion of the interior designer only. It is supposed here that, the participatory assessment approach should be applied to achieve social sustainability of the interior design by integrating the users of the interior spaces in the assessment process. This research paper applies this concept to assess the quality of interior spaces of New Aswan Language School in the City of New Aswan in Upper Egypt as a case study. The inductive approach is used here by conducting a workshop and focus discussions with a sample of primary and preparatory students. Mental maps of classes have been drawn by these students. The opinions of students and teachers about the quality of the interior design of classes, labs, and the school library have been surveyed through a questionnaire. The results clarified several problems related to indoor air quality, visual and acoustic comfort, suitability of furniture elements and color scheme used in the school's interior spaces. The present research paper suggests some applicable techniques for incorporating the principles of sustainable interior design in the process of developing the interior educational spaces. This research focuses on social sustainability which gives the user the first priority through achieving the thermal comfort, visual comfort, and acoustic comfort in the educational spaces. Additionally, the local culture and the heritage crafts should be considered and deployed in economic way in order to support the local identity and develop unique and distinguished indoor educational environments.