It's not slang, but a little casual for a teacher in French, since in France you would have to use the 'vous' to address someone you don't know really well or of higher 'rank' so what you want to ask your teacher is 'comment allez-vous?' (How are you using the vous) you can hear the pronunciation here ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-ceB-zKnGq8A.htmlsi=UAr9Df_M-87hDSC2 Hope this helps, Santé 😊👊
