The free options have all the material that is needed. Tutors are needed for kids who will not be able to block out the time for it and/or have difficulty focusing on the material during the time allotted for prep.
The best prep is still taking the test in real conditions. Some kids can do that on their own, and others do need somebody to make sure that the conditions match those at a SAT/ACT test.
Another thing to consider, which is often ignored, is that kids often are missing material. Until a student has covered pre-calc and had at least two high-level English classes, they may simply lack the knowledge needed to score very highly on an SAT. The SATs are not “ability tests”, they are test of mastery of language and math. No matter how well a kid learns how to do on standardized tests, they still need to know the material on which they are being tested.
That should also be a consideration when choosing a tutor/prep classes. A tutor who claims that their students increased their SAT scores from Sophomore to Junior years by “an average of 60 points” is taking the credit for the material that the student learned in class. The same can be said for claiming the credit for their students having an average of 50 points higher scores on the SATs than on their PSAT/NMSTQ.
Another thing to consider is that “an average increase of 50 points” says little, since an increase from 1050 to 1100 is not the same as from 1400 to 1450, and the difficulty in raising an SAT from 1400 to 1450 is much higher than from 1050 to 1100. Since there are difference in how difficult SAT tests were, an increase of 50 may also indicate differences between the tests. Finally, a 50 point difference may be the result of a good night’s sleep.
The best candidates for tutoring are kids who have mastery of the material, but not of test taking. SATs especially require mastery of the material but also mastery of taking SAT tests. Kids whose mastery of the material exceeds their mastery of test-taking, and have difficulty acquiring that mastery on their own, will benefit from a tutor.