In Prince Caspian (Chapter 12) and The Voyage of the Dawn Treader (Chapter 13), characters mention Aslan's death in Edmund's hearing and he doesn't react in surprise, so I think it's safe to assume he was told. 

I'm not sure whether I'd have told Edmund if I were Susan or Lucy, but I think C. S. Lewis included their little exchange about it to get readers, like us, thinking about it. 

Posted by: @col-klink

I'm not sure whether I'd have told Edmund if I were Susan or Lucy, but I think C. S. Lewis included their little exchange about it to get readers, like us, thinking about it. 

I think you're right. The conversation definitely stuck out to me as I just finished rereading LWW. I don't know if I'd have told Edmund either. What a difficult thing to have to explain! I feel that he should know- at least, he has a right to know and it might be beneficial for him to understand, as it would help him to understand the importance of our decisions and how good and loving Aslan is. Even though it would be terrible to know (and to perhaps feel responsible for such a thing), I think if I were Edmund I'd want to know. The better understanding of what occurred would surely affect my future choices for good, I think. Still, I can't imagine telling (or even how to tell) that to Edmund if he were one of my siblings.

I think Edmund was told at one point. In The Horse And His Boy, he says,

“It is very true. But even a traitor may mend. I have known one who did.”

Posted by: @jasmine_tarkheena

I think Edmund was told at one point. In The Horse And His Boy, he says,

“It is very true. But even a traitor may mend. I have known one who did.”

 

I really love that quote, and it is one of the ones I thought of when I was trying to remember whether there was evidence he was told what Aslan did. But while it shows that he knows he betrayed his family and has changed, I decided it didn't seem to me to prove that he knows that Aslan died for him so much as it is Edmund acknowledging his own mistake and improvement. I agree, though, that he likely was told. Do you think that was a good thing? Would you rather know or not know if you were in Edmund's position?

“Does he know,” whispered Lucy to Susan, “what Aslan did for him?
Does he know what the arrangement with the Witch really was?”
“Hush! No. Of course not,” said Susan.
“Oughtn’t he to be told?” said Lucy.
“Oh, surely not,” said Susan. “It would be too awful for him. Think
how you’d feel if you were he.”
“All the same I think he ought to know,” said Lucy. But at that
moment they were interrupted.

I feel like when Susan said "it would be too awful for him", that was just Susan being Susan; looking out for her brother after everything he had been through.  At this point, that information probably would have been overwhelming. Did it mean 'never'? I personally don't think so...

The main point that I got from her reluctance was that it wasn't Lucy's place to tell him, or Susan's, or anyone else's.  It was between Edmund + Aslan, on Aslan's terms.

That being said, I would be surprised if he didn't find out eventually, especially from examples highlighted elsewhere in the thread - a really fascinating discussion! Thanks for bringing it to the forefront, @rainyweather!

Honestly, while I feel Edmund ought to know, it's such a hard concept to explain. I wouldn't want to be the one to tell him that kind of news until he was able to process it. I would rather have had Edmund find out by himself after a few years and slowly take it in and accept it. 

If I was Edmund, I would want to know. However, although I would want to, I feel that that would only increase my guilt on betraying my family. With Edmund though, even though he learns such hard news, he chooses to grow from his mistakes and becomes wiser. That's really one of the main reasons why he is my favorite character.

This is one of the points where this story doesn't correlate with the Gospel story; Lewis was wise not to have Aslan dying for the whole of Narnia (although the White Witch does threaten what would happen to Narnia if a traitor was not killed), and to make it personal for one child. In fact this makes a more understandable point for children!

I think Edmund needed to know and would have understood one day, in his adult years as King Edmund. However I don't think that the girls would have been right to tell him.

I always felt that it should be left up to Aslan as to whether or not he was told.   I think, though, that he probably heard it from someone else (not a Pevensie) over time.    

I've always assumed that Edmund eventually did find out what Aslan did for him, although there's no indication of when that happened and who told him. I forget where I read this, but there's at least one Narnia commentary that points out that in VDT, there's this exchange between Edmund and Eustace after the latter's un-dragoning...

"... Between ourselves, you haven't been as bad as I was on my first trip to Narnia. You were only an ass, but I was a traitor."

"Well, don't tell me about it, then," said Eustace. "But who is Aslan? Do you know him?"

"Well — he knows me," said Edmund. "He is the great Lion, the son of the Emperor over Sea, who saved me and saved Narnia...." (emphasis added)

The fact that Edmund describes Aslan as the one who "saved" him, as well as Narnia, does seem to imply that he now knows about Aslan's sacrifice for his sake. We're not given any more to go on than that, as far as I'm aware.

Posted by: @coracle

This is one of the points where this story doesn't correlate with the Gospel story; Lewis was wise not to have Aslan dying for the whole of Narnia (although the White Witch does threaten what would happen to Narnia if a traitor was not killed), and to make it personal for one child. In fact this makes a more understandable point for children!

I think Edmund needed to know and would have understood one day, in his adult years as King Edmund. However I don't think that the girls would have been right to tell him.

I always felt the fact Aslan dying for one, making it a personal sacrifice, was a great way to explain the Gospel to children. Because it makes it more personal, like "if it were only you, He still would've went through with it". 

There's no way Edmund was never told. Maybe not at that moment, but he certainly had to have been aware. He seemed, in my opinion, to be aware of it even if not outrightly stated. More hinted towards, which I think makes it more powerful. Susan probably felt it wasn't their place to tell him, but nothing states Aslan didn't tell him. And a side note, I always thought it was interesting how Edmund's title was "The Just". He was a traitor, and yet he would be known as Edmund The Just. It's beautiful.

I think it's pretty clearly implied in VDT that Edmund did know. At Aslan's Table on Ramandu's Island when the Stone Knife was mentioned and Ramandu's Daughter confirms Lucy's suspicion that it's the same knife Jadis used to kill Aslan, it's mentioned that Edmund had been looking uncomfortable at the conversation..