When did it become cool for teenagers to dress like skanks?  When I was in high school, turtlenecks, plaid shirts and J.Crew rollneck sweaters were all the rage.  Like modern day Amish, every inch of skin covered, Lahser High School was somewhat the face of Preppy In America.  Nowaday, 16-year-olds are running around in skinny jeans (if you're a dude); so tight that if they are wearing underwear, you can read the darn size tag.  Girls are parading around in camel toe spandex pants and cropped shirts.  This is like a bad parallel universe where we are in the 80s but not awesome Molly-Ringwald-Erasure 80s.  

Don't get me wrong-- spandex pants rule; I wear them all weekend long.  Spandex should not be see through.  I don't want to see your underpants, or your nether regions if you're not wearing underpants.  Spend the money, buy a decent pair with full coverage, and by full coverage I actually mean not sheer.

As for skinny jeans....  Guys should just not wear them.  No dude looks good in skinnies.  An already scrawny teenager will look even more gaunt with tight ass jeans.  Paired with large high tops-- the skinny jean look will take you from looking stupid to even stupider (is that a word?).