An abbreviation for "Progress Report."
For those who do not know what a progress report is, it's a notice sent home mid-marking period of a school quarter or semester. The progress report (progrep), notices the parents of their child's ill-doings in school and bad grades.
"Dude, i got my progrep today..."
"Nice man, wanna hang today?"
"Did you not just hear me... I got my progrep today..."