Having something tangible that belongs to mother is a link to her, a kind of talisman that can be taken out and looked at, or fingered in a pocket for comfort, and if it is something that she will need, which has to be returned to her, it reinforces the idea that he will see her again at the end of the school day.
Dog owners do the same kind of thing when they leave a piece of clothing with a pet while they are away.
Retiring and living frugally in money from downsizing after years of stress


the thing is his teacher has not changed her hair style 

