Wear shorts in Fort Smith Public Schools!

Okay so I went to school and I'm starting a new school. Well anyways, I spent almost 150$ on shorts. I was there 2 days In a row and today they told me no shorts allowed. Where I live it's super hot! And 90 degrees all the time!!! We have the right to wear shorts?! What's wrong with it? Also nothing in the handbook states 'No shorts' just nothing exposing Underwear! Please sign so we can wear shorts it's hot! I also saw a girl wearing pajamas. So you can wear pajamas but not shorts?!