I, like many of the other repliers here, was a straight A student prior to entering the Nursing Program. But as Compassion_X mentioned, A students better get used to getting B's, and yes, even C's (this was a hard transition for me, believe me).
Nursing school is way different than conventional college classes. Sure, you'll be required to know your stuff, but when it comes to tests, it's not just about regurgitating what you just read/heard in class. It's about critically thinking things through! I've seen many B/C pre-nursing students do fantastic in actual nursing classes, because that's just how their mind works! They weren't very proficient in memorizing pages of facts, but they could critically think like there was no tomorrow.
Keep your head up, do NOT get discouraged... especially over A-'s. I'm graduating 2nd in my class, and I only got ONE A in all of my nursing classes! The rest were B's and C's (mostly B's
) Good luck, you can do this!