Here are some points you can use,
1) teenagers mind set is just like a mud, what impression you would put on it, they will keep.
2)teenagers gain all kind of knowledge, positive or negative.
3) its a fact, that we are a slave in hands of media.
4) media helps in globalization.
5) media don't have boundaries, so teenagers can gain some kind of news, which might be harmful for them and can affect their mentality.
6) media helps the teenagers to know about some critical issues, in which their opinion is important.