So, let me see if I got this right....you're saying "fuhgettaboutit". Am I right?I am going to be the poster you’d rather not hear from. Most times our parents know best and we need to abide by their decisions. They are able to see the “bigger” picture where maybe you are not able to yet. IMHO I also suspect that they have picked up on clues that you are not quite yet responsible enough to singlehandedly care for living things.
I would continue to work and do things around the house, yard, etc. that show your parents you are becoming a more responsible person. Chickens do take a lot of time and money if you raise them as pets and raise them correctly. Since you do not live on a farm where farm chores are already a given, I would suggest you spend these next few years experiencing life. Like @ChickenCanoe said, you still have a long life ahead. In the meantime, if you are really serious and committed to keeping chickens, do all the research you possibly can do about chicken raising, illnesses, feeding, housing, euthanasia, and so forth. Get a little side job and save every dime you can, even if you don’t need to. There will come a time you’ll be thankful you did all the research and I suspect there will come a time when you’ll be thankful your parents said “No.”