That you will have to work out with parents, they have to be convinced you have the responsibility and commitment to care for such animals. A long term commitment, as piggies can live up to 8 years.
They are also very social animals and need to be kept in pairs or more.
A single male perhaps would be demanding of a lot of your time to be the missing companion.
Your piggies may be around by the time you do college, what then, and what of your social life.
A proposal here, maybe consider a couple or few mice, or a single hamster. they are better for the school times mostly sleeping during the day. They rarely live over 3 years, but if you don't care for them properly, they can get to smell bad. Again, it is a responsibility thing, do it right or best not do it at all.
I rescued a baby mouse, my mom only had one rule, if he smelled, he was gone, had him 3 years and such a wonderful pet.
Your dog,,I see no reason you can't form a strong bond with your dog, maybe you take over with the grunt work. Hard to beat the loyalty of a loving dog. No pet is something you just put aside like a toy when the novelty wears off, and that will happen with any pet, even a pet house spider.