The Bailey School Kids

Vampires Don't Wear Polka Dots by Debbie Dadey and Marcia Thornton Jones (1990). Story does not seem dated even though it was published 18 years ago...
*3rd, 4th, 5th grades. Story moves quickly, appeals to boys and girls.
Highly recommend this series
The third grade class at Bailey Elementary was so bad, they had run off several teachers. All that was about to change when principal Mr. Davis introduced red-haired Mrs. Jeepers. She wore a polka-dotted dress with a green broach that seemed to glow. When a child began to act out, she rubbed her broach and instantly order was restored. Except with Eddie. He flew paper airplanes, chewed gum, burped and still Mrs. Jeepers remained calm. The children thought she must be a witch or a vampire. Two of the students sneak into her house one night to inspect what might be a coffin-they saw the movers haul it into the basement when she moved into the creepy Clancy house. They reached the box but couldn't open it. The next day, Mrs. Jeepers says her sleep was disturbed by burglars... was the teacher sleeping in that box? It is left to the readers' imagination.

Finally, Eddie is acting up so badly one day, Mrs. Jeepers takes him into the hall to speak to him. He returns but is very pale. He promised to never make Mrs. Jeepers mad again... her green broach never glowed the rest of the year.