I would definitely recommend that any 7-11 year olds read ‘Alex Sparrow and the Really Big Stink’ By Jennifer Killick. The main character is called Alex-obviously!-, and he and his friend Jess were both given superpowers with horrible side effects in the hope of finding out why their friends at Cherry Tree Lane School are turning into weirdly polite and well mannered pupils.
This is a fast-paced, funny, action packed book and was really fun to read!