It may depend on how many students in the school take the SAT/ACT. In Colorado the ACT was used in 11th grade as the ‘No Child left Behind’ test, so everyone took it, even many kids in special ed, students who had only been in the country for a year (ELL), kidts who had no desire to go to college. Some schools have averages of 17 or 18.
In Wisconsin when I was in high school, test scores weren’t required to go to Wisconsin colleges (not sure if that’s still the case) so hardly anyone took the test. Our hs, with one of the biggest graduating class sizes in the state, didn’t host the test and if you wanted to take it you had to drive about 45 minutes to another town. In my sister’s class, only 3 kids took the SAT and they were #1, 2 and 5 in the class; the SAT average for that school was quite high (the three students went to Harvard, MIT and Middlebury).