Step 1: Read the situation.
While teaching, a student asks a question that is not related to the lesson. What should the teacher do?
Step 2: The guiding idea.
A good teacher should keep students curious but should also protect the flow of the lesson. Both goals must be balanced.
Step 3: Why not be harsh.
Punishing or ignoring the student would kill curiosity and may make the child afraid to ask anything again.
Step 4: Why not stop the class.
Answering a fully off topic question right then would break the lesson and waste the class time of others.
Step 5: Find the gentle balance.
Asking the student to meet after the class respects the question and still keeps the lesson on track. The child is not discouraged, and the class is not disturbed.
Step 6: Final answer.
The teacher should ask him to meet after the class.
\[ \boxed{\text{Ask him to meet after the class.}} \]