I used this worksheet to have the students get in pairs and compose a short 2-measure melody. The rubric for the composition is at the top of the paper.
It was then sight sung by another pair of students who would be graded for how well they sung it.
The worksheet is designed to be cut into three pieces for paper conservation.
Each pair of students write the melody in a given amount of time. (I would give them two minutes) They then exchange papers with another pair of students, who grades and practices sight singing the melody. (I would give them two more minutes to do this.) They then exchange the papers another time, and the last pair of students sight singing the melody for a sight singing grade. (I would give them another two minutes to do this.)
I would also sometimes collect the melodies and scan them into a Power Point Presentation so the whole class could practice singing them, and then I would randomly redistribute them so the kids could sing them in pairs for an assessment.
The requirements in the rubric can be changed to make it appropriate for more or less advanced students.