I took off a semester in the middle of nursing school to join the reserves. Once boot camp and SOI was done, I went right back to school. Just remember if you do this while in school you are rolling the dice when it comes to activations, drills, and AT. Your military obligation trumps and school obligation you may have. It may be better to finish school and start working and then join if you so desire. You can also look into an MOS that doesn't require a lot of time to train for, unless there is something specific you want to do.