If I want to get my G.E.D and I'm a minor if my mother says I can get it can a school tell me I can't get it? Or is it still completely up to me and my mother?

There are requirements to get a GED, one is age, years out of school and other factors, If you are still of the age where you are suppose to be in school,

So the GED program will have their requirements that have to be meet.