Pupil (on phone): My son has a bad cold and won‘t be able to come to school today.
School Secretary: Who is this?
Pupil: This is my father speaking!

Teacher: What is the axis of the earth?
Student: The axis of the earth is an imaginary line which passes from one pole to the other, and on which the earth revolves.
Teacher: Very good. Now, could you hang clothes on that line?
Student: Yes, Sir.
Teacher: Indeed, and what sort of clothes?
Student: Imaginary clothes, Sir.