Is Piggy fully aware of how far from "civilized behavior" Jack and his followers have degenerated in Chapter 11 of Lord of the Flies?
No, not all. Piggy convinces Ralph that they should go and meet with Jack to get Piggy's glasses back. He sincerely thinks that Jack will be convinced because returning Piggy's glasses is simply the right thing to do:
"I'm going to him with this conch in my hands. I'm going to hold it out. Look, I'm goin' to say, you're stronger that I am and you haven't got asthma. You can see, I'm goin' to say, and with both eyes. But I don't ask for my glasses back, not as a favor. I don't ask you to be a sport, I'll say, not because you're strong, but because what's right's right. "
Piggy falsely believes that Jack will listen to reason, that he will make decisions on the basis of morality. He fails to realize that Jack has not heeded the conch, or reason, for some time now. Ralph tries to tell Piggy otherwise, that Jack and his tribe will be wearing warpaint and will be like savages, but Piggy will not listen. Right before Piggy dies, he is still talking into the conch and trying to the appeal to Jack and the tribe's reason and morality:
"Which is better--to be a pack of painted Indians like you are, or to be sensible like Ralph is?"
This question alone shows how much Piggy has underestimated the savagery of Jack and his followers. He gets his answer--a response that kills Piggy and stuns the reader.