Toads by Midnight. The Swamp Adventures, #1

All Ms. Pickle wanted to do was to get back into teaching without having her dark secret uncovered, and all the three mischievous fourth-grade boys wanted was to continue playing baseball and pulling pranks on their classmates and teachers. But the magical force in New Orleans brings them together, and Ms. Pickle becomes the new teacher at Croaker Charter School. The boys suspect magic when they can't seem to outsmart their new teacher who seems to be always a step ahead of them, making their pranks backfire.
The boys set out to investigate Ms. Pickle and discover her dark past. They had no idea she had to refrain from using magic at all cost, but when Julio, Sean, and Michael pull another dangerous prank that puts their lives in jeopardy, Ms. Pickle decides to use her powers to save them while teaching the boys a lesson that's not part of the fourth-grade curriculum.