I guess it's case by case. I know of an Iranian girl who came to Switzerland (Zürich) on a Schengen tourist visa some 3 years ago and decided to stay in order to learn French (she was not interested by German, in parts maybe because for her, Swiss-German was a very ugly-sounding language) so she went to the office cantonal de la population of canton Vaud and was successful in changing her status without the need to go back to Iran. She now has a B-permit...