Dogs are a lot, lot, lot of work.
I had forgotten how much work they were when we got Cali last July. See, when we had our previous dog, I was 5, and I didn't remember the process.
Puppies, any dog really, will cry and whine for the first few nights home and I mean all. night. Cali did this for about two weeks, I slept on the floor beside her bed some nights. She sounded so pitiful and scared, that I stayed with her, and I didn't get any sleep. Eventually she started only crying in the early morning, and now she doesn't at all.
Potty training is really frustrating, too. You have to be around the dog 24/7 making sure you stop it immediately if they start to go somewhere in the house and take them outside. Dogs won't understand if you reprimand them after the fact.
Then there's the other training. Sit and stay are important, as well as trying to make sure it won't jump up on people, bite, etc.
My puppy chews through everything, she's got crazy sharp teeth, and even though she's a beagle, she needs toys meant for dogs much bigger than her. The first few days she: chewed through wires, dug into our leather sofa, and my other dog was obsessed with remote controls (taking the buttons out).
You have to research how much to feed your dog, and how much they need to be walked. And you must be diligent in both of these areas. We don't walk my dog much because of how much we play with her during the day (she constantly needs attention).
Not to mention the fact dogs are expensive. Food, toys, beds, carpet cleaners, trainers, bowls, tags, licenses, leashes, vaccinations, spay/neutering, and the actual price to adopt. Even if you rescue a dog (slightly cheaper than buying purebreds), the medical bills alone may add up.
In short, getting a dog is not a decision to be taken lightly. You'll be at school most of the day, don't kid yourself that you can take care of one to the attention it needs. Your parents need to love dogs too.
Remember: dogs are not accessories or fun playthings. They are living creatures who need plenty of care and if your whole family doesn't support the decision, it's not a good idea to get one.