弟弟 new school bag

弟弟 starts his school with my old school bag. That bag is too small and not able to keep many books.
Since he behave well for the past 2 weeks, mommy promised to buy him a new school bag.
At first, he insist to use the old school bag. This is 弟弟 pattern, he always do something opposite to what he said.
However, after a day, he likes his school bag and wants to carry by himself.