I never really thought of this saying as an idiom; as I have heard it so many times and to be honest I have never really thought about it fully. I have lived this idiom over the last few days; as a lot has changed within my life and ‘TEFL’ life.
back to the drawing board
time to start from the start; it is time to plan something over again. (Plans or schematics are drawn on a drawing board. Note the variations shown in the examples.)
It didn’t work. Back to the drawing board. I flunked English this semester. Well, back to the old drawing board.