Derogatory term used to describe one's crappy local community college. The community college is seen as both lacking in real collegiate educational value and additionally using no discretion in its acceptance of every single applicant. It is described as the 13th grade to imply that it is merely an extension of public high school. It is considered only one step above going to beauty school or training in air conditioning and refrigeration repair.
"Judy didn't get accepted by Trenton State, so she's going to the 13th grade"