What classes is he taking?
Are the classes weedout (ie., introductory classes for engineering or pre-med at a large university)?
A 56 may be a C with the curve of the middle students are in the 50-60 range. However this student is at the bottom of his classes.
He may be overwhelmed and not dare tell his mom. He may not realize what’s happening (if he doesn’t check his online grade portal, he may not know his grades - some exams are multiple choice in an exam center which administers the test. The professor doesn’t “go over” the test in class like in high school, that’s what office hours is for. )
Is there still any possibility he add a “sports” or “study skills” class for 1 credit so that he remain full-time even after dropping one class? Indeed, remaining full time is crucial (below 12 credits may mean students have to reimburse financial aid, may mean losing dorm room…)
Registering for 16 credits including one ‘easy’ class or module makes the 4-credit drop possible.
Ask him whether he’s gone to office hours, for which classes, what happened (he you’d go with highlited notes and questions on things he’s not sure about from the lecture, the lab, the readings). Has he set up tutoring hours?
Teenagers fall prey to “magical thinking” whereby believing in yourself and occasional study would be sufficient to success in college.
If the grade is on a curve, a bottom grade means a D and two Ds for 8 credits could mean probation.
He needs to turn around now. Let him know what he needs to do and say you want to see C’s or higher on the next tests.