Apple Tree is a staple in the elementary music curriculum. I have developed my own unit to use this song as a review for my students at the beginning of the year. We start with a fun game and then move into the heart of the unit.
The unit covers rhythm identification (ta, ta-di/ti-ti, and rest), solfege identification (sol, la, and mi) and has an ostinato and Orff arrangement that can be used.
Assessments can be added at any step of the way, just by listening to your students sing, watching them perform rhythms, and observing them on the instruments.