Here's a round that fun to do with your upper grades.  It's great because it contains ti, which is a melodic element that I focus on in 5th grade.  It's "eerie" without being Halloween based, so if you have students that don't celebrate Halloween this will work for you.

Here's the round:

I took four levels of Kodály at Portland State.  But when I did my masters at Colorado State University (with a Kodály emphasis) not all of my credits transfered and I took levels II and III (again: with Sue Liethold-Bowcock and Ann Eisen).  During choir at level II @ CSU Ginger Littleton used a choral arrangement of "Old Abram Brown" that was essentially the round, with ths coda (tag) at the end:


The kids love this round.  AND it works great on concerts!