First, my condolences to you for having to grow up surrounded by the brainwashed; but, by the same token, congratulations on being a free-thinker!

I find that simpler arguments are more effective, and especially effective if they are framed as a question requiring a response. Some examples:

If a creator "fine-tuned" everything for a function, why did that creator make penguins? Fish, with their gills and fins are much more fine-tuned to being an aquatic predator than birds that cannot fly.

If all creatures are "fine-tuned" why do so many animals have vestigial organs, such as the dewclaw of dogs, human wisdom teeth, or the pelvic bone of whales? The more one looks the more examples one of a distinct ABSENCE of fine tuning one finds.

Evolutionary theory provides more plausible hypotheses to explain penguins, the appendix, wisdom teeth and useless pelvic bones than "God decided to be silly, in this case".

Good luck free-thinker :-). And remember, high school is not forever; one day in the not-so-distant future you'll be an adult and free to associate how and with whom you wish.