A couple things wrong with your post-
1. You said your parents are over protective and won't let you outside.. How will you give your dog the exercise it needs??
2. If your mom "hates animals" then who will bring it to the vet and groom it?? I mean, you can help with these things but I don't think it's fair to expect your mom to do the bigger things in the responsibility if she doesn't even like animals. How about a pair of rats? They can be in your room, don't need to go outside to pee and you can train them to do things. Plus, your mom never has to see them! You can play with them in the room.
A dog is a big commitment. Let me tell you. I was 10 years old when we got my dog. It was a cute family pet until he grew up and needed walks and training etc... After we moved to an apartment he needed 4-5 walks a day (because he was a terrier and we didn't have a backyard). Guess who, out of 5 people, had to walk the dog?? Myself and my younger sister. Mom, dad and my other sister got sick of taking him out.
That dog lived to be 14 years old. That's a lot of time and patience put into a small dog with little social skills (can't just let him run in a field bc he would start fights with dogs and bite running children) and a lot of money on toys (which he destroyed) and food (good quality food never runs for less than 15$ a bag)
ANyway, I'm not trying to discourage your decision to get a dog. ANd I think it's unfair your mom said you could have one if you got A's. I feel like she set you up for failure somehow. I would like you to be happy with what you have and respect your parents' authority.
I'm looking forward to finishing school so I can another dog too. Right now, in this small apartment and doing full time school I think it would be unfair to get a dog now. That's my lifestyle though.
Anyway, keep your head up :)