Underage magic isn't just magic against the law, but it's also magic that happens on an accident. The magic normally happens under 11 unless your a late bloomer which your magic is likely to reveal it's self later on or it could show up early but the normal age is seven years old. The magic is not from a wand, and instead it's usually from you when your in a situation with a accident. For example: someone sneezes and a vase breaks and after that some flowers start to grow. But just because something happens which seems like magic, it could also be a coincidence which to find out if your signs are not a coincidence, some other magical signs or the same one should happen again soon.