Demon Defenders: Classroom Demons by Jake Lancing
Alex, Inch, Cherry, House and Spit are a gang of five football-loving, mischief-making friends - who just happen to be angels. But the gang get into one scrape too many and are banished to Earth until they can learn to behave. Stuck with a teacher who makes Professor Snape look like Mary Poppins, the gang's chances of returning don't look good - especially when they discover a demonic plot right there in their classroom.