It really depends on what sort of teacher you have. If they're easy-going, make jokes or tend to go off-topic, you'll be fine with the second answer given.
If you have a teacher who likes making people conform to rules, always gives homework no matter what, or hates it when people joke or are casual, go with the first answer given.
The biggest tip I can give is this: ALWAYS APPEAL TO THE PERSONALITY OR WHOEVER WILL BE MARKING YOUR PAPER. If you don't know their personality, always go with a more formal approach, and don't use slang (like kids, instead of children).
Dude, this thing was posted in 2009. I think her essay is LONG overdue by this point.