Each school submits a high school profile to each college. A high school profile tells colleges about your school. Here is a sample from the College Board. The profile explains what courses your school offers, the demographics of the student body, what the average GPAs are, and provides other information a college can use to assess how competitive your school is and how well-prepared students from the school are.
To see your high school's profile, ask your guidance counselor or look on your school's website.