I preach layers. Not only can layers make a bold and eclectic fashion statement, but they can also serve to maintain warmth. We know this from all of the turtlenecks and sweaters we (okay, not me, but many people) pile on in the winter. I figure you can always add more.
Be practial, but still get some extra mileage from out-of-season-but-still-in-size items already stored in the closet.
Last weekend I found this great little red cardigan from Gymboree at a local consignment shop for $6.00. Although I'm not really a huge fan of red, I was immediately struck by the pink and orange embroidery on the front, and knew it would have a very practical place in Samantha's wardrobe. Wanting to bring new life to a pink sundress (purchased 2 years ago at a thrift store for @$2.00) that I don't even recall if my daughter worn last summer, I layered it under the sweater to bring out the pink embroidery, and over a pair of jeggings (oh, how it pains me to type that word, silly as it is, but eh, what else would I call them?). I just love ruffle details, and I love experimenting with layers! Topping the outfit off with a pair of boots, she looked as ready for school as any other child this time of year. The cardigan is made of a lightweight cotton that will carry through to the summer months, and this look would have worked just as well over a regular pair of jeans, with the cuffs rolled to just skim the tops of the boots.
Of course, you may be saying that you live in the frozen tundra of the north, and that's fine, too - like I said, you can always add more. Put a long-sleeved shirt under the sundress, or just layer for the outdoors by adding a fleece hoodie before putting on a heavy winter coat. I'm reasonably certain it is not a frozen tundra inside the classroom.
Got a favorite short sleeved shirt of your son's that you'd like to get more mileage from? Layer a long sleeved tee underneath, ala Big Bang Theory (only without the geek factor), and a hoodie over top. (Can you tell I love hoodies?)