Again, really depends on your kid. We had my son take a practice test that we paid for at a site like in 9th grade. His school doesn’t test early like some schools. We found out he had a pretty bad reading comp issue. Got him help and always suspected this.
He didn’t want to prep summer after sophomore year. Lots of his friends did and took the Act in the fall of Junior year. Most were one and done. He took his later Junior year. He took it 3 times to get his final score. One was a practice test but did need a tutor for ACT timing. It was really fast for him and why the retakes. But on practice tests he scored really well.