It shouldn't be used for he/she or to connect words/ideas or to contrast black/white.
So, he or she sounds better. Words or ideas. Black or white.
And instead of a student/teacher study group, write a student-teacher study group. (The hyphen wins in formality).
Of course, in other cases, using the slash is more acceptable.
It is sometimes used for dates, though still considered informal (1991/92 or 10/15/18).
It is a shorthand for per (10 km/h).
It is used in some abbreviations (n/a).
Simple enough.