Fan Casting Mage Born of Muggles in Sort by Tropes

A Mage Born of Muggles is someone who is born with powers despite their muggle parentage in a setting where Magic and Powers are passed on genetically or are the birthright of a Mage Species. Of course, they will still need training in how to use their power, and so they will quickly meet someone from the Magical Society, who will take them as The Apprentice, lead them to Wizarding School, or otherwise ensure that they're introduced to their new life.