I have a 13 year old ds and have seen on his phone KIK conversations between him and his girlfriend (also 13) about 'how far they would go'. They have been together nearly 10 months now.
He said he 'would like to have sex' 
but she said she would not want that until she was 16. He also said he would only do 'whatever she felt OK with' .
He would also like to 'feel her tits'. She said 'I haven't got much to feel' 
Plus lots more about blow jobs, hand jobs, fingering etc etc etc.
I did not tell him I had seen it. He would be absolutely mortified.
I imagine this sort of conversation is common place between them and their friends. In fact, I know it is!
I am not worried. They don't really have the opportunity to have sex and I honestly believe a lot of it is just talk. If it came down to it, I doubt, for all his chat, he would actually do it. [niave]
I suppose it's different though, when they have only been seeing each other a month. I would try not to feel 'furious' with the boy though. It is normal and common place to say these things at that age. She just got found out!
I agree that a conversation needs to be had though. But from the girls point of view, not a 'what a horrible boy' point of view iyswim.