Y people get ready?

No what I mean is why do people get ready for school like last three days or last days because, when I went to the the market to buy some of my mother's stuff and I see a crowd of people who want to buy stuff for their kids for school.



 But, I don't get why do people buy their stuff on the third last day or the last day. They are so wired and you know what I am talking about. Do you buy your stuff on the third last day or the last day.