How to explain the difference to a class of 12 year olds, asks my teacher niece. She tears her hair out at confusing physics concepts.
Google describes average speed as total distance travelled over total time. Average velocity (a vector) is the resultant displacement vector divided by elapsed time. They are neither conceptually nor (often) arithmetically the same.
My niece is really struggling to find the best way to explain to her class the concepts of scalar and vector. In fact these concepts are anchored within the frameworks of linear algebra and vector calculus (studied at university).
In general, the meaning of any quality in physics is defined by the equations in which the quality participates: at school level the mathematical background just isn't there, so concepts all-too-frequently come across as arbitrary, badly-grounded and confusing.
I have a lot of sympathy with her.