I would suggest you make this decision on the basis of two pieces of information. There is probably not enough room for improvement to justify the high cost of a course. The primary value of such a course lies in its provision of disciplined preparation. I also think that you should be very suspicious of any claims or guarantees that a prep course will improve your test score dramatically. Gerald Lee Wilson.
Nothing is deducted or subtracted for wrong answers.
There is no penalty for guessing. You will often find you do not have enough time to complete every question. It is not unusual to find you are not able to finish each section of the test without a certain amount of guessing. While individual questions do vary in difficulty, each correct answer makes the same contribution to your score, regardless of how easy or difficult it may be. Within each section, questions are not arranged in order of difficulty.