I'm doing some pulley problems with some 7th graders but mine are a little different.  They are all rescue systems for rope rescue.  The one I'm trying to do is a 9:1 lift system with 4 pulleys, 2 of which are tied to an anchor, & 2 of which are attached to ascenders.  One end is connected to the load (typically the rescuee) & the other end is attached to the people doing the lifting (rescuers).  If you think of 2 "z"s connected from the tail of one to the head of another, that's what the system is like.  I have it set up in the classroom to do but I wanted to make sure I have the force diagram right.
O = Pulley        r = ascender (allows rope to move in 1 direction only)
| = Shows connection between pulley & ascender.  Normally Pulley is attached to ascender with a locking cabiner

 Load  -----r-------------------O(Anchor)
                |                  ----
                |          ----
                |   ----
                   |               ----
                   |       ----
                   O--------------- Rescuers Pull Here