Kindergartener and still breastfeeds

My good friend has a son who is about to start Kindergarten in a few weeks.. and she still breastfeeds him! Is this weird? Is it even ok? What are your thoughts? She has told me in his lunch pail she will pump milk in a water bottle for him to drink.

P.S : she has two younger ones ages 1 and 3 and she also breastfeeds them as well