[NOTE- the following is in the context of U.S. laws and events, and the situation may differ in other countries, or even parts of the U.S.]
Ammo and schools are a touchy subject.
There is a very real chance that some ignorant teacher or administrator will go totally nuts, and the resulting circus will include police, fire, bomb squad and all the news media in town. Evacuate the school and neighborhood around it “for safety” and they might take the case away somewhere to blow it up (hey, it’s fun and they don’t get to play with their toys much).
You really need to chat with whoever is in charge at the school in advance, and preferably get their written approval, to “bring in a non-explosive empty artillery case as an historic artifact. to be removed at the end of the day.”
It should not be this way, but it is in most American schools these days, and many other countries are probably equally silly. Like Virginia Tech which canceled a traditional blank firing rifle salute in honor of Veterans Day. Like schools that go nuts if someone brings in a toy soldier holding a gun, or chews a cookie into a pistol shape.
History is badly warped, if taught at all, and it has largely been replaced by politically correct nonsense, so younger people and “educators” are easily frightened by unfamiliar stuff.