Moving this to here as I didn't pay attention to the rules ;w; my bad.
"I have a homebrew setting where pretty much anything outside of wizardry and general clerical magic is very illegal, like to the point of being either killed, confined or deported out of the country. Likewise, one of my PCs is playing a draconic sorcerer unaware that his magic is actually sorcery, subclassing into wizard.
How could I reason in-universe that he's been able to live his life and perform magic without being found out? Any advice is greatly appreciated."
To clarify: The player is aware that his character is a sorcerer, and wants this to be a component of his story. When I say subclassing into wizard, I intend to mean he's spent some of his life studying arcana/wizardry in-universe and is mechanically taking wizard levels. That's was a bad on my part.