RPG's for Kids, not Teenagers - Kids. Whilst there is the rare child who can play RPG's in a collective and co-operative manner (I've known just one) there seems to be a real trend (especially with 4e D&D) to run games for very young children.
Uri Kurlianchik has been posting articles on the official D&D Website, about his experiences running games for Kids - and whilst his intentions are no-doubt good, I don't think they are entirely realistic.
The OLDEST player he has been running games for is 11, and (to me at least) 11 is the YOUNGEST (unless they were exceptional) aged player I would run games for. His youngest Player is 7 (and doing surprisingly well according to Uri) which is really REALLY young to cope with the concepts of even the simplest RPG.
His lastest article D&D Kids: Punishment made me really smile, as its a perfect example of why running D&D for young children is NOT a good idea.
The article basically deals with controlling the players behaviour when they "act up" - and Uri categorizes them into different types -
The Astronaut - A kid whose oblivious to the "rules" of the game world, forgets what he can and cannot do - probably because his attention span is poor.
The Crybaby - The Kid who always looks like he is on the verge of tears or a tantrum, ALL the time over everything.
The Cheater - I think this needs no descriptive explanation.
The Serial Character Changer - Who constantly wants new characters, either because he finds something cool in the Manuals or is bored.
The Hyperactive - Constantly "in motion' and won't stop still.
The Joker - Actually a misnomer for what this Kid is, a malicious little bugger out for a "laugh" all the time.
The Chaotic-Stupid - A Kid who's behaviour "in game" gets his party killed repeatedly.
The Antagonist - The type of Kid who ALWAYS argues with authority figures.