I am sorry you feel like you weren't taught sufficiently. I went to a private vocational school, but they had a very high expectation. I had so much hammared into my head, that I felt well prepared in the field.
12 years later in the LPN to RN transition program it is INTENSE. I am in class with a lot of girls that graduated in the last 5 years, and they are barely passing (riding the 80 line when 78 is needed to pass). Meanwhile, I have an "A". I still recall things hammered into my head!!
Yes, going back to school WILL help you, it will NEVER hurt you. However... you may want to consider your knowledge right now, because if you feel like you weren't taught sufficiently, you may have a difficult time in the transition program which will hurt your confidence again...
Look into a refresher course... Or get a saunders RN NCLEX book
and start reading through it. This will help you prepare for the transition course, which is always extremely intense!