"Ceci n'est pas un procédé de design."
The Design Council's Double Diamond diagram is an excellent model to use to learn about design processes. However in practise it is virtually impossible to follow step by step as the process of design is deeply messy and more free-flowing because many things are unpredictable when you are creating something new. . Trying to run design projects in schools in a one size fits all process can be impossibly stressful to staff and students, however the structure of a timetable and external assessment criteria results in a compromise.
The All Design interactive design process* has proved useful in the classroom when pupils are learning to understand how one activity will yield useful material to feeds into the next process, and how by attempting to do them in the order shown to appreciate how they might flow together will improve the quality of their work and the depth of their design thinking. Conversely we also teach that design work may start at any point in the double diamond, and may well move back and forth between the two as work progresses: it is perfectly appropriate to get to any stage in designing and realise that more work needs to be done on a previous stage in order to make further progress.
Outside of the classroom excellent design very rarely happens in this sequence:
(*Ceci n'est pas un procédé de design!")