What are some good chatting sites?
Chatroulette and Omegle are two good ones.
I don't understand why you want to stop chatting on chat portals? I think chat is a social activity where one person can share his/her ideas with other peoples around the world, it is important for social behavior of peoples if they are chatting with others. I know some good chatting sites where you can chat free without any spam chat. For example chatfunk.com, allindiachat.com.
Online isn't the only place for teens to chat for free. There are a few chat apps that can be found for both Android and iOS mobile devices. Online, there are a multitude of places to chat for free like widely used social media networking sites, or topic specific forums, or even sites specifically for open chatting that have age specific rooms.