My daughter, who is now almost 31, had this problem of not being able to choose shorts and pants at various times in her schooling.
In primary school, track pants were an option for girls in winter at the public schools she attended. At one school culottes were introduced for the summer uniform, just as she moved to another school that had only dresses.
In secondary school, many schools did not give a pants option for girls at all. She ended up deciding between two schools on the basis that one offered a pants option for the girls’ winter uniform. The school that she did not choose, (a private school) still does not offer a pants option.
As my daughter has cerebral palsy and feels the cold, having a pants option for the winter uniform was essential for her comfort.
*name changed for privacy reasons