Support visual learners to structure their plan clearly — using the fair-test colour code and a strong labelled diagram.
Colour-code the plan
Students use the unit's variable colours — amber for the changed variable, green for what's measured, blue for controlled variables — to highlight their own planner. The colour pattern lets them (and you) check at a glance that exactly one thing is changed.
Diagram first, prose second
Encourage visual planners to draw their labelled circuit diagram (using the conventional symbols) before writing the method — the diagram becomes a scaffold they describe in words. A clear, correctly labelled diagram is one of the assessed criteria.