A directory is put together by humans. A search engine is compiled by a piece of software. Thank you KS, that does explain a lot actually. I have not found one yet. I wind up making up my own to fit the needs of the teachers.
Educators love to copy others in their school if they see something new.
Ram you have a question. Bushroot, everyone studies in different ways. I find it helpful to take notes on what I read or hear in lectures, then put away the book, and study the notes, and then copy downt he main points from the notes, and study the condensed version, until I get it all the way down to keywords. Others may have differign methods. The rest of the stuff I just fit in.