I am currently working on a graduate research paper and statistics is not something I'm good at.

In my proposal I need to compare the STAAR test scores of two schools. The demographics of the schools need to be representative of the average Texas school. African American 14%, Caucasian 35%, Hispanic 48%. The remaining 3% fall into the other group.

How much variation can I have in the percents of the students so that there is a minimum statistical difference? How do I determine that?

On other important number is the Economically Disadvantaged Students, Texas data says its in between 52-55 percent.

Because of the variation can I assume an acceptable variation is built in?