Sometimes outdoor is colder than indoors at my place, but I placed my bunnies outdoor cage in a spot that have shadow most of the day and keep their ears damp.
My outdoor bunnies will dig burrow/ hole and lay in it when it becomes warm. They use the damp dirt as a cooling spot.
You can always put a bit berries in the water that you have frozen and soak the veggies, during hot days it’s important they get water. You can also freeze bottles with water and place it in the cage, the bunnies will lay next to the frozen bottle to cold down. Make sure to have a few frozen water bottles in the freezer during hot days and change them during the day. The frozen bottles work wonders and it will also be like an Ac around it’s area. If the bottle is placed up on a metal or a tile, the bottle will work as a conduct and cool down the tile or metal plate. It can become a comfortable place to rest on.
But you can also see if you can ask your parents during really hot days, that your bunnies can spend time in an area indoors to help cooling them down. Specially during the warmest time of the day.
I know my parents first only allowed my bunny to live in the bathroom and later my bedroom but I could later expand their area. So you can always see if you can meet in the middle with your parents.
Off topic: I had a bunny that during really warm days would bath then sunbath to get dry and later sleep comfortable in the hole he dug. Downside with that routine was the whole lawn having small holes all over and him escaping to jump into the creak and coming back home soaking wet
I miss that silly boy, he liked playing with water during warm days (he had black fur, so he dried up fast).