Ideally, you should have taken your first practice test at the start of the course. The second test should be taken somewhere around week 6 (though it's fine to do it a week earlier or later). The third one should be around the end of the course.
Several things:
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.
So please don't think you need to start taking a bunch of CATs - that's not an efficient use of your time. After you take a CAT, you can
easily find at least 2 to 3 weeks' worth of improvements out of your results / performance - and those improvements don't come while you're taking another CAT. They take work before you can see the results on a CAT. Honestly, if people are studying in the right way, and don't have *severe* timing issues, they can typically get away with taking 3 or 4 CATs over the entire length of their study.
Read this article:
http://www.manhattangmat.com/articles/a ... roblem.cfmAnd then take a look at these (one for each problem type, examples of how to use the above analysis strategy):
http://www.manhattangmat.com/articles/GMATprep-SC.cfmhttp://www.manhattangmat.com/articles/CR-assumption.cfmhttp://www.manhattangmat.com/articles/a ... estion.cfmhttp://www.manhattangmat.com/articles/a ... roblem.cfmhttp://www.manhattangmat.com/articles/a ... roblem.cfmIt sounds as though you might not have taken any CATs at all yet; if so, take your first one as soon as you can. Take it under 100% official conditions so that you can be as assured as possible that your results (and the data) are as valid as possible. That means doing the essays and taking just two 8-minute breaks between the major sections.
When you're done with the test, you can use this article to help you analyze your results and figure out what priorities to set from there:
http://www.manhattangmat.com/articles/e ... -part1.cfmIf you have questions about how to fix certain weaknesses or anything like that, talk to your teacher or come back and talk to us here (or both!).
Also, at the end of the course, eligible students can sign up for a Post-Course Assessment: the teacher looks at your practice tests and gives you advice about what to do after the course is over. This is a GREAT benefit and you want to make sure you're eligible. In order to be eligible, you have to have taken 3 CATs over the length of the course and you have to have taken them under normal timing conditions (unless you are somebody who qualifies for extra time - then take them under whatever timing conditions will apply for you). So take that first CAT right away. (Teachers will sometimes be flexible and let you sign up if you've only taken two CATs - but it's up to the teacher. The main concern is making sure the teacher has enough valid data to give you credible advice.)