M.W.
My kids are 7,11,13. They choose what they wear. Most mornings in the early Fall and early Spring, I see them open the door, stand outside for about 15 seconds then come back in. They then choose to take a sweatshirt or not.
They are still wearing shorts and t-shirts to school...and occasional sweatshirts/sweater after their "15 second weather determination test." There have been a few days they have come home and told me they were cold at school. I never tell them what to do. I just ask them what they plan to do the next day to solve their dilemma.