In an ESL class I was teaching, a student (Congolese) suggested a dictée exercise. That such an exercise exists suggests to me that French orthography isn't wholly regular.
Precisely ! The dictée is a typical exercise which exists only because the language is irregular. Most people in France dread this particular exercise, since you can’t win - points get deducted for every mistake, most people will make at least one, and if you make enough mistakes you get 0 points whether you made 5 or 500 mistakes.
Dictations exist in German as well, and German is very regular. In fact, the German primary school teachers I know do far more dictations with their classes than I ever did growing up in England.