Exiting a list of screen sessions

[Marc Lanctot]

Typically I run commands on servers and let them run for some time.. 
when I'm done I kill all the processes with one command.

I would like to be able to kill all my screens in one command as well, 
so I thought of parsing screen -r and sending a "kill command" to each 
screen, but I can't find anything on how to do that in the man page.

I tried

  screen -S id -X exit
  screen -r id -X exit

with no luck.

So, how do you kill a screen session given its session id?

Marc
--
Human knowledge belongs to the world.
  -- Teddy Chin in 'Antitrust' (ref: open source software)