Sentence:  Observe what sanctions the teacher employs with her class in order to enforce the rules. Are individuals kept in after school, for instance, or are they asked to <WSD>stay behind</WSD> at the end of a lesson, or reprimanded in front of the other children? 
Meaning of the word marked with <WSD> tags:  To remain in a classroom or school at the end of teaching, especially to receive punishment.