Once the war was over, the Seven went to school together. Piper would often fall asleep in class, and whenever the teacher would wake her up, she'd sleepily Charmspeak "Five more minutes."
The students all wondered how she could do that, whenever they fell asleep in class, they got sent to detention.
Her Charmspeak came in handy in more ways. Whenever one of the demigods got detention, she'd simply tell the principal that they had better things to do. He was always quick to agree.
They had to stop once Athena moved to the school as their arithmetic teacher. Not only did Charmspeak have no affect on her, but it seemed as though the goddess could sense whenever it was used.