My D’s HS did a practice ACT in 10th grade, not counted, and then test prep the summer before junior year and before school in the Fall of junior year. Most students took the PSAT Fall of junior year and then the state required ACT in the winter.
The school didn’t recommend practicing with an official test because back then there were still a bunch of schools that required all attempts to be reported.
I personal don’t see the point in paying to take an official test when you can simulate timed conditions with old tests.