A good reason to: 1) select a non-gangster-ish knife, something that can never be mistaken for a weapon. SAK or traditional Case for instance; 2) not otherwise act like or hang with gangsters; 3) become involved in Scouting, outdoor club, hunting, or some other activity that requires a pocketknife.The general thinking is only a gangster would have a knife on him.
If you're under 18, your primary 'job' in life is to obey the Ps' house rules. They say "no knives", then it's No Knives. Not worth the hassle nor the consequences, if you know what I mean.
Best Wishes,
-Bob