The tower of...

I had thought that if one could convey the very basic principles then so much of science can be explained so easily. For example, if fundamentals of electromagnetic spectrum can be laid-out then so many things can be readily understood (I don't mean to start from Maxwell's euqations, but that light in any form can be understood with a single concept of EM spectrum).

This, I found doesn't work in the class. Children simply fail to sense the magnitude of how fundamental the electromagnetics is. They are unable to see the path which appears to us as a grand short-cut from our learned point-of-view. To that extent a subject-expert may have a disadvantage in the class-room.

For most part, your goal in the class is not to unify information (that comes later) but to demonstrate the diversity of phenomena. In the present example, one will have to show students various things that happen to the light first-hand from radio waves to x-rays.

While its the business of science to unify diverse phenomena into smaller set of fundamental rules, the full sense and understanding of this comes only as a hind-sight. For most of the school life the focus is only on one brick at-a-time and view of the tower to be built. The tower of knowledge has to be constructed brick-by-brick, lots of bricks.