Teens are in a turmoil of hormones, passage into adulthood, and all that. Not easy to keep them focused, or to teach them patience...
I think that one should not give in to this restlessness, but remain in a calm alternative to it. Teens might seem to disapprove, but they often really enjoy the ingredient in their lives.
Nonetheless, they need to get a lot of their energy out, and will be pleased with a training that makes them pant and sweat a lot.
Usually, they enjoy throws more than pinnings, because of the action bit - and the way it allows them to show off their agility and daring. Well, this may be more true for boys than for girls.
And they're usually much more openminded to the spiritual aspects of aikido than one might assume.