I guess it depends on how you test and whether you are able to study on your own or you need a bit more structure.
I test fine and didn't use a study center; they're expensive and I figured I didn't need it. I am also a pretty good self-starter when it comes to school stuff--usually

.
Some of my classmates who struggled a bit on tests used a study program and it worked well for them. Some of them took it over the break before the last semester started and that seemed to work very well.
Honestly, a lot of the NCLEX test is being able to understand
how they want you to answer the questions. It wasn't so much based on knowledge.