Unfortunately, "specific" and "NJ knife law" do not belong in the same sentence. I have done some research on statutes and case law, and there's a lot of grey area. Specifically, the following are illegal: switchblades (autos), dagger, dirk, gravity knife. There's also a very (purposely?) vague section on "dangerous knives", where no clear definition is given. The problem I have is with the definition of "gravity knife", which includes a description of centrifugal opening. This is why I keep my knives very tight in the pivot area. Someone with good technique can flip open just about any knife, but mine cannot be construed to be intended to open in that fashion.
Of more concern for you is your age (I checked your profile). At 16, you need to be VERY careful with anything that can be construed as a "weapon" - especially in school. With Zero Tolerance rules, I wouldn't advise you to carry a nail file to NJ schools. On the outside, if you are caught with it while doing something wrong, no matter what size or shape it is, it will be considered part of the crime (i.e. it goes to your intent to use it in a criminal act) and you will have an added weapons or "armed..." charge. If you are minding your business, the best that would happen in that situation is that the LEO would confiscate your tool, so don't go spending a lot of money.
The following does not constitute legal advice, but I'll tell you what I do...no fixed blades, folders with blades <3.5", (usually closer to 3" max), with tight opening actions. Bear in mind I am a 30-something married father of 2 with a respectable job in an upper middle class area, and my carry habits are very conservative. As a teenager, you need to be even more careful. That's just how life is sometimes.
For research, try Bernard Levine's link o state laws, or go to:
http://www.njleg.state.nj.us/
...the applicable statutes are in 2C:39
Also go here to look up case law by keyword. Pretty slim in this area, but interesting anyway:
www.lexisone.com
Welcome to the forums, and be careful out there.