I am a college admissions counselor - PLEASE take my advice as what is best for 90% of students.
Take the ACT/SAT first WITHOUT test prep. Test prep CAN cause a student to door poorly on their first test. It's a mental thing -students, and their parents, and their test tutors all get psyched up - psyched out - and the student gets nervous and panics.
Take the test first without pressure, without ANY LEVEL of score expectations, and without preparation.
This allows the student to be acclimated to the test environment, and the test format.
When the scores come back, the student, parents, and test tutors will have a much better idea as to how their test prep time will be best spent.
I experienced something similar assisting a student last year - both of his parents are teachers - and they let him take the test his first time with no pressure - he scores a 26 - which is a decent score by nearly all measures. However, with the aid of a test tutor - his 2nd time taking the test - he bumped his score to a 31. He was able to prep for both his strengths AND his weaknesses - and it work out extremely well.
The biggest thing is to no stress out about it. Scores are scores are scores. I hear parent after parent after parent swear that their child COULD do better on the ACT or SAT if they would only try. Well, I hate to break it to all of those parents - if they student WANTED to do better, they would. Test - especially the ACT and SAT are great indicators of residual knowledge. That's that helps a student get through college. How much do they learn, retain, and then apply to more advanced concepts. College is not about rote learning - it is about critical thinking, application of knowledge, and grasping new concepts using foundation material as a frame of reference.
I'll get off of my soap box now!