Personally I don't like "Assistant Director" because I think people get the wrong impression of their scope ... especially the assistant director.  They feel they are second in command and in my way of thinking that falls to the SM.  Secondly, they feel they can give the director advice, or even worse, direct the actors behind the director's back.

 

As a director what I need an assistant for are things like taking notes, watching script when the SM can't, filling in for a missing actor so the SM doesn't have to, or running an errand, etc. 

 

I also don't like the term "assistant to the director", because the wording is clumsy but mostly because it makes it sound like that person is my slave ... which he/she is ... but I don't want others to know that.   I call that person a "Production Assistant".  That's vague enough that I can have them do anything.

 

We used to use have "Student Assistant Director" as a development thing for (generally) High School age kids.  However, that was worse than having an adult. Often once a kid got that title they started bossing people around.  Rotten kids.  I'm glad my wife directs the high school plays and not me.