The Worst Witch to the Rescue by Jill Murphy
Loveable but accident-prone Mildred Hubble is possibly the worst witch ever to go to Miss Cackle's Academy for Witches... 'It isn't actually a known spell. I sort of made it up myself.' Mildred Hubble always tries her best, but her spells never seem to go right. She may be the worst witch at Miss Cackle's Academy for Witches, but she's the best friend you could ever have.