That's true, However, in practice, those universities and and various other test centers may not be administering the test on the day you want/need to take it. There are many testing centers, but they do not all administer the test every time, or they can fill up before the sign-up deadline is passed. Just FYI. Sign up early and check out the various testing centers by DATE.
Is it that big a deal, though, if a child takes the ACT/SAT in a public high school?