Ho do I get my sister enrolled in school?

I am 28 years old. I am married with 2 kids. My mom, dad and 17 year old sister are living in maryland. They are going to be moving to North Carolina in November. I am trying to get my sister down to North Carolina with me so she can start school and not have to switch schools in the middle of the year. I went to the school and they said because my parents are not living her that even if she is living with me they could not let her enroll in school. I was reading on the internet that I could possible get temporaly legal guardianship of her so I can enroll her in school. I need information on what I have to do to make this happen.