Class Dismissed by Allan Woodrow

Class 507 is the worst class Ms. Bryce has ever taught. And she would know -- she's been teaching forever. They are so terrible that when a science experiment goes disastrously wrong (again), Ms. Bryce has had it and quits in the middle of the lesson. But through a mix-up, the school office never finds out.
Which means ... Class 507 is teacher-free!
A wickedly fun story, perfect for readers of Gordon Korman, Jeff Kinney, and Barbara Robinson!
Loved, good condition hardcover.