I believe that anyone can benefit from weight training regardless of age.  I even let my son which is ten years old do some under my strict supervision. 

Having said that, the BRE system was designed for people who are 13 years old or older.  I recommend for teens who are below 18 to make sure they use higher reps.  For instance, in the Loading Phases I would use 13-15 reps and in the Growth Phases I would do between 10-12 reps.  The reason for this is because most teens under the age of 18 still have some growing to do and training with good form at higher repetition parameters will prevent any damage to the growth plates that may hinder any growth.  In addition, teens under the age of 18 should also refrain from doing more advanced techniques such as forced reps.

As far as results, the best gains always happen on the teenage years due to the high levels of anabolic hormones produced by the body.  It is through my teen years that I gained most of my muscle mass.  Using a sound program like the BRE system during this years will yield incredible results.