Bailey School Kids #7 is Aliens Don't Wear Braces. The school gets a substitute art teacher named Mrs. Zork, and she acts strangely. She's obsessed with colors, and the kids begin to suspect she's an alien, sent to steal all the colors from Earth.
This book was pretty good, especially the showdown scene between Mrs. Zork and the vampire teacher.
The kids break into Mrs. Zork's house, and they discover a spaceship. She claims it is a pottery kiln. In the dramatic showdown, Eddie starts pushing all the buttons on the machine to get Earth's colors back. Not long after, there is a huge explosion in the sky. Everyone assumes it was unplanned fireworks, but our heroes know it was the alien spaceship exploding.
The next day, Mrs. Zork has disappeared, and I really hope she was an alien, because if not, the kids just blew up her house for no reason. How unexpectedly violent of those third-graders! There is a full, two-page illustration for the explosion, too.