These are the best wooden rulers I’ve seen as a teacher. They are thick (really, the thickest rulers I’ve seen), made from high-quality wood that is sustainably forested (FSC certified wood), and has both inches and centimeters.
The thickness of this ruler makes it sturdy and break resistant. I feel like a child would really have to purposefully be putting in a lot of heavy duty effort to break these.
They also have a hole drilled in the end for hanging up in a locker or clipping onto a desk, notebook or binder.