Volatile friendships

I have two boys in my class who are good friends, and worst enemies. Transitions are difficult for both of them, and we never get through circle without them screaming at each other. (Like, red-faced, top of the lungs screaming, with lots of “I hate you, I hate this school, F you” thrown in.)

I do a heavy work activity as our pre-circle transition, which they enjoy, but makes no difference in behaviors. Less structured free play time (centers, outdoors) tend to go smoothly and they play and enjoy each other.

What can I do to support these kids? Keeping in mind, transition is often the only trigger, and from there on if they do so much as lock eyes, it’s mean words and screaming.