Received a PM asking me to respond. I'm sorry I'm just getting to your message now; I've been on vacation since 23 June.
Generally, GMATPrep is the most reliable practice test (because it is the real thing). MGMAT practice tests have a standard deviation of 50 points, so ours are pretty good too. (The real test is about 30 points.) I don't know the SD of Princeton Review tests.
There are bigger issues we need to discuss here, though.
First, are you taking these tests under full official conditions, including essays? If not, then your score is not as valid. How far off it might be depends upon how much you deviate from official testing conditions - for example, skipping the essays often results in an inflated score, especially on verbal.
Second, it's pretty much never a good idea to take tests more than once a week - and, most of the time, you should only be taking tests every 2 to 4 weeks. CAT exams are really good for (a) figuring out where you're scoring right now, (b) practicing stamina, and (c) analyzing your strengths and weaknesses. The actual act of just taking the exam is NOT so useful for improving. It's what you do with the test results / between tests that helps you to improve.
When you take a test or do a practice problem, you are primarily "doing" - that is, trying to use everything you have already learned to do well on that problem / test. You are not actually
learning (much) while you're "doing." Learning comes via the analysis and review you do after you have finished a practice problem or test. Once you have taken a test, you're wasting time if you take another test before you analyze the first one, set up a study plan based upon your results, and then actually learn what you need to learn.
This article talks more about how to set up a study plan:
https://www.beatthegmat.com/mba/2010/02/ ... study-plan
This article talks about how to evaluate an MGMAT test:
https://www.beatthegmat.com/a/2009/09/23 ... tice-tests
And these two explain how to analyze practice problems and how to learn from your errors:
https://www.beatthegmat.com/a/2009/10/09 ... ce-problem
https://www.beatthegmat.com/mba/2010/04/ ... our-errors
Once you look through those articles, you'll see why it can take 2, 3, even 4 weeks to learn everything you want to learn before you take another test.
Re: your quant score, a math degree likely means you'll do well, but it doesn't mean you'll necessarily score in the 90+ percentile right from the beginning. This test requires you to know the math, yes, but it also requires you to know how to take this test - and after only a week of studying, you can't have mastered that yet.
You mention studying for SC using OG12 and "some materials from this forum." OG12 is a great source for practice, but it does not actually teach you how to get better at any part of the test. I'm not sure what materials you are using from the forum, but if you are going to score 40+ on verbal, then you need things that actually teach you HOW to do the problems and HOW to improve. The above article about developing a study plan talks a bit more about this issue.
So, start with the above, take a look through everything, then come back here and let us know what you discovered about your strengths and weaknesses and what you propose to do for the next several weeks or month for your study plan. Then we can start to talk about the details and make sure you're on the right track!
