I'm not aware of a precise analogue for the broad category, "professionals." In AE, at least, we tend instead to be more specific. For example, we sometimes label a particular space as "belonging" to a particular group, e.g., "teacher's lounge" or "executive dining room". Or we might put an "X Only" sign on it, e.g., "Doctors Only".
But I can't think of a general phrase for such things.
I need to translate "Espace Pro" on a tourist office website.
On an equivalent site I saw "Trade Area" but this sounds a little odd to me.
In my context, "MICE" or "Business" or "Tourism professionals" might work, but I think I will just use "For professionals" (which I also saw on a similar site). Hope these suggestions help someone.
P.S. Old Novice, unless one teacher is very lucky and has a whole lounge to him- or herself, I think you meant "Teachers' lounge"!