Are you asking about:

• Jain teachings suitable for a 12‑year‑old?
• How a 12‑year‑old can start following Jain dharma (puja, pratikraman, vows, etc.)?
• Some story or Jain book recommendation for a 12‑year‑old?
• Something else related to a 12‑year‑old and Jainism?

Please tell me a bit more so I can answer properly.