I have this issue too. Lilith's board is missing and I lost the boards for a couple of Sims. I just studied for hours each day and they all got A+ actually, so I guess if you study enough it will bring the grade up. Too bad it can't be bought though.
Note to Self: Never drop out if there is a presentation board in the inventory. You can't delete them? :o ohhh that would drive me crazy. I sometimes like to empty my inventory... foods in the fridge, treasures in the treasure chest, books on the shelves, items on display, flowers in the flower bench, I sometimes put the homework and diaries in the bookshelves or on desks. Feels good to empty the inventory. I could not deal with a presentation board stuck there, no
