Many of them have that little fold-out file that could be used as a weapon.
As 'the' standard of what is and isn't a weapon, the TSA won't let you on the plane with even the ones which don't have that file.
Fear my pencil! Seriously. Even sharpened, that little fold-out file will not penetrate as far as a Cross pen or mechanical pencil of good quality, and is not nearly as dangerous as the western-style belt buckle I normally wear on the end of a (roughly) three foot long leather strap (belt), properly wielded.
If we eliminate everything which can be used as a weapon, we have people in velcro attached straitjackets in a rubber room in restraints.
While that might make the warehouse keepers happy (as often as not, that is what schools are, a warehouse for the children of two-paycheck families), elimination of all the pointy things or other things that can be used as a weapon is just not possible. Even the power cord for a laptop can be used as a garrote, and a well torn pop can provides a foot or more of sharp edge, albeit unwieldy, which can be wrapped around anything stiff to produce a slashing weapon.
For the imaginative, virtually anything can be used as a weapon, if that is the intent, but there is so much else the average person would carry (even on a plane) which would be a better weapon than the fold out file (or just the nail clippers), I always found that particular ban to be pretty ridiculous.