Musical Opposites

My 1st/2nd grade class has been learning about forte/piano, fast/slow, and high/low over the past few weeks.  Forte/piano and fast/slow went really well.  We've only spent 2 periods on high/low, but I'm confused because some of them just really don't seem to get it...  I think 50% is maybe English miscommnication somewhere, and 50% is maybe that 1st graders can get easily confused.  But it's possible that I'm missing a step somewhere too.  Any help?

Here's what I've done:

• Today we read an awesome book (thanks, Liz!) that had pictures and voices of different animals.  After I read, we talked about which animals spoke in high voices, and which spoke in low.
• We've spoken chants in high and low voices.
• We've sung in high and low voices. (Ok, not too much)
• We've looked at pictures of different things (tigers, birds, man, woman, drum, flute, etc), made the sounds, and put them on "high" posters and "low" posters.
• We've put our hands on our heads for high, and hands on our laps for low, while listening to very obvious low and high sounds on the piano.
• We've danced around, moving high and low, listening to an obvious recording of high and low sounds.

After thinking through this now, I think most of them get it.  But any help for the ones who are still a little clueless?  At least they're cute. :)

--Kate