Yes, kids are capable of comparing their behavior with their peers' behavior and drawing conclusions. They are capable of making observations - this is commonly known as socialization. Often kids are more observant and more perceptive than adults think, starting at very young ages. While signals can easily be crossed within the peer group, kids learn a ton of information from others their own age.
Although children aren't as mature as adults, I believe that they can absolutely pick up on the behavior of their peers. Kids are like sponges, and they soak everything up. Peer pressure is the best example of children judging behavior. While some kids do give in to peer pressure, most kids understand when things are wrong and why they shouldn't do them.
If kids were good at judging the behavior of their peers, they wouldn't be so quick to follow along with the pack. Although some children do have well-developed instincts, most haven't yet developed the maturity necessary to deviate from the group even when a small inner voice tells them that something's wrong.
Kids are not always good at judging peer behavior. They do not always understand the complex logic behind why people do the things that they do, and have a tendancy to misjudge their peers. This is why kids pick on each other and have fights that seem silly to adults.