Reclassifying

Anyone know what the real rule is and why PREP schools are still allowing players to reclassify? Are grade exception forms still needed when a player goes to prep school. Technically if you go from High school to a prep school you are suppose to continue to the next grade and if you choose to you can do a Post grad year to strengthen your academics to be more prepared for college. However if you are no longer reclassifying how can a prep school fill out paperwork saying you are a grade exception? Anyone understand this?