Often referred to as a tute.
Tutors are often students themselves, volunteering their time to fulfill one or more of these objectives:
a) Fill their resumes or
b) Actually help kids or
c) Make money
Whether in it for a, b, or c, most tutors know what they're doing.
Sherry: I can't. I'm tutoring.
Samantha: You mean smoking a bong?
Sherry: No; I tutor kids in subjects like algebra and writing. Like a teacher?
Samantha: But the internet defines a tutor as a bong!
Sherry: Not anymore.