A recent study suggests IQ is not stable during teenage years as was thought but shifts in step with changes in particular brain areas:
http://www.guardian.co.uk/science/2011/oct/19/teenagers-iq-scores-adolescence
Why teens are prone to risk taking:
http://www.cnn.com/2011/10/19/health/mental-health/teen-brain-impulses/?hpt=he_c1
some tips on how to motivate your teen:
http://www.howtolearn.com/2011/10/motivating-teenagers-a-survival-guide
And general tips for dealing with teens:
http://o5.com/4-tips-for-dealing-with-teenagers/
http://www.kvue.com/news/health/kids-doctor/132513818.html
http://www.semissourian.com/blogs/parentscorner/entry/44185/?response=no
http://www.emckemptville.ca/20111110/lifestyle/The+teenage+brain+-+a+time+of+great+change