I used to wear a chainmail shirt to elementary school. The teachers never knew what to do about it because there was no section in our dress code forbidding medieval armor.
… Where does an elementary school child get access to an actual shirt of chainmail sized properly for them?
Growing up as a historical reenactor meant that my parents are friends with lots of people who make chainmail. My godsister received a real rapier in fourth or fifth grade, so our unsupervised outdoor playtime was… formative.