An Inquiry on Grade Point Average (GPA)

When American schools say GPA, do they mean for a single year, or for all of your high school years combined?
I ask this because I’m worried that my 9th and 10th grade years will hurt my chances if they contribute to the overall GPA-thing.

<p>GPA means your overall average from all years. But many colleges in the United States do not count your 9th year grades. In fact, many recalculate your GPA altogether based on their own individual point system.</p>