Keeping Freddy after school

When I was teaching school I had 14 pupils. Thirteen of them walked to school or rode their horse but one--Freddy--had a mother that drove him to school. He was a cousin to one of the families in the school and was a little spoiled. He did not always behave. One day he was just awful and I needed to punish him. I could keep the other kids after school and they never needed it but Freddy was another problem as his mother was always on time. On the day he was especially bad I told him I was keeping him after school. While the kids were out at recess I changed the time on the schoolroom clock. I let the kids out all but Freddy and he sat at his seat very surprised. At the correct time his mother turned up and I let him leave. I never had trouble again with Freddy.