Sounds like a very stupid question but do colleges look at your cumulative GPA of three years (9-11) or do they look at your GPA for every year?
Most colleges will look at your grades from 9-11th grade and possibly mid-year Senior to determine your GPA based on their criteria. There are several colleges that only look at 10-11th grades such as the California UC’s and CSU’s so it really depends on which colleges you are targeting.
The GC reports this on the School Report. Yes, it’s cumulative, up to whenever your hs last calculated it.
Then adcoms look at the transcript for 9-11 and 1st semester senior year. They can see grades and rigor, your successes or stumbles. Since you have some high aspirations, know that grades less than A can concern them that you might be less prepared for the rigor at that college. This matters most for hs courses related to your possible major and least for classes like gym or drivers ed.