Welcome!

You've received great advice above. I'll just add that in general the rule for when to prep for a test is as follows:
If it is an IQ/ability test, do not prep (Yermish article on Hoagies).
If it is an achievement test (such as the ACT), prep using materials supplied by the test maker.

Students interested in prep for ACT will find materials, freely available to all, on the ACT website: http://www.act.org/products/k-12-act-test/
- Question of the Day
- Sample Questions
- Test Tips

The amount to prep might best be determined by the student's curiosity and interest in spending time prepping. smile