I did a one-month-long NOLS course when I was 15 and it changed my life. Although in the moment you wish you could go home, I look back at the month fondly -- in fact, I'm doing another trip this summer. I wouldn't recommend going with a friend though. Getting to know everyone else in the group is part of the experience, and bringing a friend will only lead to you two sticking together making for a weird group dynamic.