The age of enchantment

"In Whetherwhy, everyone has magic inside them -- grown from the changing seasons of spring, summer, autumn and winter. But a rare few are Enchanters: people born with magic in their bones, who can wield all four seasons of magic. When Juniper discovers she is an Enchanter, she is invited to study at Thistledown Academy. Unwilling to be left behind, her twin brother, Rafferty, follows her to the capital city of Stormgrove and takes up an apprenti...