My Daughter Strained Her Ankle. There Is No Bruising, Barely

My daughter strained her ankle. There is no bruising, barely any swelling, it only has mild pain to the touch in a small area, even if pressed. I've been having her elevate and ice it and giving her anti-inflammatory medicine. I had her take the next day off from school to rest it and then today I sent her back with a pair of crutches. The school said she needs a prescription for the crutches or she cannot have them at school, for safety reasons. She is a straight A student and has NEVER had a behavioral problem. There are time constraints as she has school tomorrow, so I can't make a typical doctor's appointment for her. So I either have to pay the crazy fees at an ER just for a prescription for the crutches and for them to tell me to keep it elevated and iced, or she'd have to walk around without crutches possibly causing further injury and pain (not an option). Is there another way to get a prescription for crutches?