Witch Baby and Me At School by Debi Gliori
Lily is 9. Her sister Daisy is 1. And she's no ordinary baby. Somehow, when she was born, something went rather wrong... and now Daisy is a Witch Baby. Nobody knows this but Lily - she's the only one who can see when Daisy makes the fridge float in the air, or turns people into slugs, or summons up her very stinky dog Waywoof... The sisters have now settled into their new home and so it's time for Lily to start at her new school. Can she survive being the new girl? Will Daisy be a help or a hindrance...?