Even though there are plenty of other standardized tests for younger students like ACT Aspire or the PSAT, there are still many middle schoolers every year who take the ACT. 7th grade is definitely a bit earlier than most people take a college entrance exam, but it's possible you might have to take it as part of an academic talent search or want to take it to see what it's like.
Just as good 7th grade ACT scores are different from what good scores would be for juniors or seniors, though, 7th grade ACT prep is very different from high school ACT prep. Find out the best way to A-C-E the ACT in 7th grade in this article.