Because of the way Music Works 1 begins with a melody and then creates harmonies by combing melodies, most students start off with some kind of polyphonic texture. This is wonderful for creating harmonies but can be the most difficult kind of texture for sustaining a longer section.
I find that the Texture Lesson in Music Works 1 is essential for helping students create homophonic textures. I put a lot of attention on homophony of the kind where their is a clearly defined background part with a melody above it.
I use a number of classroom performance strategies enabling kids to perform homophonic textures and then have them create an entire section in their piece that uses homophony.