His mother read to him about 20 different sins from an examination of conscience for kids
His mom said he sat there thinking very hard as she was reading them, but he didn't say anything. She wasn't sure what he was thinking, but she kept going.
When she finished, he looked up and said "Wow. I've done all of those!"
From the mouth of children!
P.S. - as a follow up, I asked him how his first confession was. He told me, smiling ear to ear "I felt a LOT lighter"