Lucy it obviously depends on the teen, but those I know are very very aware of how fake news etc works. And they discuss it in real life, in class, with friends.
It's not surprising - my dc has been aware of at least two general elections, the Scottish referendum, and the EU referendum. To this age group, politics is real, it directly affects them, and they are starting to feel empowered.
They listen to the radio, they read the BBC news website, but they read widely. Not just one paper.