Call of the Crow (Skyborn #2)

"In the Clandoms, everyone is born with wings, though not all the clans are treated equally. Ellie Meadows longed to become a Goldwing--the knights who protect the people--but because she came from the humble Sparrow Clan, her dream faced almost insurmountable resistance. Nox Hatcher has it even worse. Nox is a Crow, a shattered clan. They can't own businesses or run organizations, all due to a mysterious betrayal made hundreds of years ago. Nox has had to steal and scrape just to survive, but a single goal has kept him going, even when it felt like all the Clandoms were against him. Years ago, his mother was imprisoned for a crime she didn't commit. Now, finally, Nox is going to save her. But there's more to Nox's story than even he realizes, a secret that's been kept buried for centuries. And the king of the Clandoms himself is so desperate to conceal it that he's sent a ruthless assassin after Nox and his friends. The four young fugitives must watch every shadow. If they aren't careful, they'll be cut down before they can rescue anyone"--Dust jacket.