I have had 2 children go through SAT/ACT testing. The first we did the whole prep class, extra materials etc for... She took each test twice, score didn't change too much each time, even after extra help.
Second child decided to only take ACT. Had a study guide, but no extra classes.
Both did fine, high enough to be accepted at all schools they applied to and helped to get extra merit aid.
I agree that unless they are trying to get into a very selective school, don't stress over it. Many colleges and universities don't even use the scores in their admissions anymore. Grades in school and extra curriculars are what they look at.