It's all about the layers, A wind-breaker in case of surprise showers/wind over top of a cardigan and long pants/capris. Once I get to school, a cardigan is still usually just right. If it's too cold, I can always order tea to warm up bit. Sweatshirts are a bit overkill still. Throw some mittens into my bag and I usually arrive not too chilly just yet.
I try to keep my wardrobe balanced for the day. I'll wear a quarter-sleeve shirt with a scarf, jeans, and boots for the chillier days and take off the scarf if I need to. Or I'll wear a t-shirt/ tank top and jeans with a cardigan that I can remove later as the day warms. Or sometimes, if it's warmer, shorts and a long-sleeved shirt.