What test is skipping from 8th to 9th grade called?

I want to skip a grade because my twin sister is a year ahead of me.

My son skipped a grade, but there wasn't exactly a test specifically for determining that. The headmaster, school counselor, and his teachers evaluated his progress, entrance placement tests, social skills/maturity, classroom performance, and enthusiasm for learning.

Maybe it's different for your school/district? Ask a teacher or a guidance counselor what the process is in your school.

Oh, and before you get your hopes up too high, make sure your parents are on board, and have a compelling argument for why they should let you skip... and "my twin is a year ahead of me" isn't a compelling argument.