I've seen a lot of threads lately that ask the question, "What can I carry into/around/on fill-in-the-blank and still be legal but not vulnerable?"
One thread had a reference to the OP's school regulations that stated specifically any edged item not used for food preparation was "verboten".
While I was in chef school (see where this is going?), I was issued a set of knives made by R. H. Forschner. I soon remembered where most Martial Arts weapons came from: They had originally been tools of farmers who had had their legitimate weapons banned by the Japanese Tokugawa Shogunate around the end of the Warring States period. Tonfas were threshers, Kamas were scythes, Nunchaku were also used to thresh, Bo staffs were used by almost everyone as walking staffs and boat oars, etc. I began to think of different trade professions that would yield some rather vicious "Found Weaponry".
We are surrounded by tools that could very easily become wicked-sick weapons of mass agony and discontent. Hammers, screwdrivers, crowbars, box cutters, heck, even the items they are intended to be used on could be used in a defensive role. A pipe of sufficient length could act as an escrima stick, or even a short staff should the need arise.
I used to carry my knife-roll (a kind of roll-out bag used by cooks and chefs to carry their knives) in my weak side hand. I'd wrap my chef knife in a towel and place it in the middle of the roll with the handle somewhat sticking out for easy access. No one ever stopped me, and I never had an issue with the Police even though I was literally carrying a 10" fixed blade knife that is specifically designed to slice flesh with an artistically smooth cut!
I was essentially walking around like some samurai with his scabbard in hand and ready for whatever silliness the nearest legally-challenged moron might try to inflict on me.
I'm not suggesting that anyone carry a whole knife-roll on them, that's just not cost effective or practical. I am suggesting however that one chef knife (specifically purposed for food preparation!) rolled in a towel (bacon print!) tucked into a bag, purse, or other school/city stuff-carrier could fit the bill. If anyone asks, you cook as a hobby, and you need it for a fill-in-the-blank. It might help if you actually know a few things about cooking and throw some jargon out there as well, or show enthusiasm for this great new dish you can't wait to try out (like criminal cassarole).
Keep in mind too that not all cooking knives have to be big or even evil-looking. Many slicers (do not even think about what those would do to someone...) have rounded tips to prevent accidental pokes and sticks in the bread or meat that would ruin the appearance of the presented food. One of those would be a slash only type weapon, but I assure you...
...you would only need one slash.
I for one would never attack a chef. For one thing, most of them are scat-flinging crazy, and for another, they might very well have this tucked into their apron:
It might work for some and it might not for others. Just a thought...