Today 14/2/2019 I asked S, why do you go to school?. He took off from school today. Tummy pain, the mom said.

So the question was, Why do you go to school?

S answered : To study 

Me : Why study?

S : To get a job.

Me : Why do you want to land in a job?

S: To earn money.

Me: What do you want to do with the money?

S: Buy things, like house, food and other stuff

Then he started asking me why do I go to work?

My explanation : 

I am not working for the money, I am offering my skills and services to the world and exchanging that with the things that I need and desire. Money is just an intermediary, it's a medium of exchange