She could not sit still during the lesson and was a pain in the ass for the teacher.
During the lesson she was warned multiple times but she continued. Before the lesson was over he told he she had to stay after school and he would give her a reason to wiggle in her chair. Expecting the usual spanking she loved she went over to his class after school.
Instead of a spanking he gave pulled a dildo out of a drawer and after working it in her ass she told her the detention started.
Sitting behind her he enjoyed the sight after 15 minutes he pulled her towards him for the rest of her punishment. He was sure that after he finished the punishment it would be impossible to sit still during the next lesson.