The Dragonfly Pool - Eva Ibbotson

Tally Hamilton is furious to hear she is being sent from London to a horrid, stuffy boarding school in the countryside. And all because of the stupid war. But Delderton Hall is a far more unusual and interesting place than Tally ever imagined, and she soon falls in love with its eccentric staff and pupils. Now she's even organising an exciting school trip to the kingdom of Bergania... Although Tally never expected to meet the prince. Prince Karil hates his life at the palace and he is only truly happy when he escapes to the dragonfly pool, a remote spot in the forests of Bergania. Then Karil meets a feisty English girl who brings the promise of adventure. But his country is under threat, and the prince soon looks to his new friend Tally for survival as well as friendship...