I find it awesome that you are thinking about your goals this early in you college career. However, I would not take a semester off if you can avoid it. A tip would be, if you have the time, not to study rigorously for the lsat for 3 or 4 months like many people do. (because you are right, it WILL show up in your grades in school) Because you already know your graduation time and when you want to take the lsat, study the lsat comprehensively at a nice steady pace. If you can work with the lsat steadily for a year or 18 months, rather than vigorously for 3 months, it might serve you much better. You will gain much more experience with the lsat and retain more knowledge of the test. I have been studying every aspect of the test for about 8 months now, and I still have 8 months until I take the test. I am enrolled in 18 credit hours, and will be enrolled in that many for two more semesters. I only study the lsat when I have free time and am not needing to work on homework and such. Many people will probably tell you that you need to put in hours and hours and hours a week for 3 months or something like that. However, this is not always the case. I took a preptest when I first started studying the lsat and scored a 147. Through 8 months of steady but comprehensive studying, I am almost at a 160. You will nail the lsat fundamentals into your head if you study steadily for a long period of time, rather than hardcore for a few months.