I show it under the microscope, showing that there is really nothing to observe:





Here I actually use a "black box" as normal kids never would comprehend the function of a p-n-transition.
As we will scarcely educate former semiconductor producers I may put the declaration:

It is a complete nonsense and waste of time to fill the kids' brains with useless stuff they never can understand!
I do not know yet a good model to explain these functions and -by the way- it would be obsolete as mor and more transistors are enhanced by the field-effect technology which would perhaps easier to be explained - but has not at all found its way into school books.. Such transistor switches can be combined to so-called "gates" .

move on