I have found it is really dependent on the student and what they believe they want to do as to if the SAT or ACT is a better test for them.
The SAT is more of a general business, non-technical student in school and the ACT is more geared to those wanting to head to college in technical subjects.
My son took the SAT, he walked out saying he sucked at it, and only scored around 1890 but he took the ACT, walked out, said he aced it and scored a 31 so take both and see how you do.
The HS generally provide free prep courses, the water polo team did a fund raiser for 10.00 you got the prep course and test.
I did great, thanks. In 1963.