Why does Ms. Lemry say she'll sign Mark's drop card, but refuse to sign Jody's drop card?

Ms. Lemry let Mark out of the CAT class since Mark doesn't feel compelled to stand up for his convictions and she doesn't want it to appear as if the school is challenging Mark's religious beliefs. However, Ms. Lemry refuses to sign Jody's drop card because just wanting to be with your boyfriend is not grounds for a transfer.