What Katy Did (Carr Family #1) by Susan Coolage

When Katy Carr and her sister Clover leave for boarding school, they are weighed down by worry. How will their father manage without their help? Can they ever hope to fit in and make new friends? When the Carr girls arrive, they meet the principal, Mrs Florence, who is tall, dignified and very strict: there are no less than thirty-two rules that students must adhere to! And with Miss Jane always on the prowl to discover the slightest fault, Katy fears that it might be more difficult to stay out of trouble than she'd hoped. But then she meets Rose Red - irrepressible, unconventional and always full of fun. With the right friends, Katy can't help but get into all sorts of scrapes.