Bitcoin don't have age requirement because there's no way to identify it's users unless you have use a KYC/AML complied wallet like coinbase. If not, as long as you know how this work. You're fine.
Anyway, banks is one of the way to buy bitcoin. But you're still lucky because you can still buy bitcoin. Try localbitcoins.com. Try to find a local seller near you to buy bitcoin. Maybe you can buy bitcoin with cash since banks don't allow to use their service since you are underage. Im just curious, why don't just ask your parent to make an account for you? I think they allow that. I don't know what are the laws in your country pertaining to that matters.