Borrowing from Rocksmasher99's answer since it was getting to be a bit big of a change.
This could be the The Unwanteds series by Lisa McMann.
Summary of the first book, The Unwanteds:
Every year in Quill, thirteen-year-olds are sorted into categories. The strong, intelligent Wanteds go to university, while the artistic Unwanteds are sent to their graves. On the day of the purge, identical twins Alex and Aaron Stowe await their fate. While Aaron is hopeful of becoming a Wanted, Alex knows his chances are slim. He's been caught drawing with a stick in the dirt- and in the stark gray land of Quill, being creative is a death sentence. But when Alex and the other Unwanteds face the Eliminators, they discover an eccentric magician named Mr. Today and his hidden world that exists to save the condemned children. Artimé is a colorful place of talking statues, uncommon creatures, and artistic magic, where creativity is considered a gift and a weapon.
In the second book, Island of Silence:
Aaron Stowe has been kicked out of the University of Quill. But, he is power-hungry. Gathering a group of sympathizers named The Restorers, he plots his rise to power, and the demise of Artimé.
Meanwhile, two silent, orange-eyed children, named Sky and Crow, have arrived on a raft. While Artimé seems to continue along normally, Eva Fathom, a supposed Restorer, is spying on Quill, and passing along information to Sean Ranger, an unwanted teenager. Plus, Mr. Today starts to teach Alex how to be a head mage, and devises a plan to trick Aaron. But, the plan backfires. Aaron confronts Mr. Today. Meanwhile, Alex and Simber, one of Mr. Today's statues, go out on a search for three of Alex's missing friends, Meghan Ranger, Samheed Burkesh, and Lani Haluki. They rescue Meghan and discover that Samheed and Lani have been captured by a neighboring, silent island, called Warbler. On the way back, Simber freezes, and crashes into the sea, because of the Island of Fire. Alex and Meghan barely avoid death. At the same time, the Restorers attack Artimé, and causing mass hysteria.
The summary of the third book, Island of Fire, confirms that Mr. Today died in the previous book and this wiki entry confirms that Simber, a giant winged cheetah sand construct, falls out the sky after Mr. Today dies.