I need an example of progressive knowledge and I believe such a reference was made here at the .org about light.

By this I mean - in science classes in schools, pupils are taught about the nature of light. First the basics like particle and wave, later they have to unlearn some of it and fill in new knowledge.

Are there anyone here who remembers such a step by step knowledge ladder with light in particular?
I know I have read about this somewhere and it involved at least three steps if not more.