I have spoken to several French natives regarding this issue...their age~ 35yo
1. They use 'suivre' for "taking a French course...Je suis un cours de français and never 'prendre' for a full course. But!! I was told that if you are referring to a specific class you can say: "Je prend une classe de français aujourd'hui"
2. For "I passed my bac"... I was thought to use 'Reussir'..J'ai réussi mon bac...They said 'Avoir' is used more commonly now.
I suspect that the common usage will vary as vary with regions of the country,as it does everywhere