My daughter’s school did practice tests in class and then she took the Explore test sophomore year (I believe that was what it was called). The kids used them as guide to see the areas they could improve. ACT prep was part of the required summer work for 11th grade, and my daughter took a ton of practice tests (at home) ahead of sitting for her first actual test. I don’t think she would have been any better prepared by taking and retaking the official tests.