Below, you will find a response I gave to a young teacher who is in his first year teaching middle school choir. They meet after school. He has eight children in the program. He is looking for ideas on how to grow his program.
Here are a few approaches that I use that may give you some ideas.
For middle school children, especially those who are volunteering their time before or after school, we need to inject fun, and we need to share music with them about which we are passionate. They will sense our passion and are more likely to respond to it.
For the fun: I call it "throwing them a bone". In addition to teaching songs that encourage the traditional choral art form, I like to pick something that is a novelty in some way. For example, I use this song each Halloween.
Once I've taught the song, I tell them to bring in a flashlight. I teach them very simple choreography. I turn on a fog machine, turn out and lights and "voila", the kids are super excited. That excitement spreads to their peers, and a few more children are more likely to join.
How many other ways can you inject "fun" into their daily experience in rehearsal? I believe they need to smile and/or laugh at least once every rehearsal!
For the "passion": I enjoy teaching them songs from musicals and helping them find their inner actor! Each year, after we've participated in our state adjudicated festivals and have worked on sight singing all year, I turn the page for the final nine weeks and we produce a musical revue. During that time, I help them learn to audition, find songs that are appropriate for their voices and "type", and we explore an entirely different way to make music. I enjoy the process, and they respond to my passion. The performances they are capable of creating when they have guidance can be truly spell-binding. The technical approaches we all take (myself included) when teaching the choral music art form don't always click with middle school students. Because I love to teach about musical theater to the students, I am able to get them to dig inside themselves. There are many positive technical effects that result from this "inside/out" approach. Two of them are that the students breathe more deeply and sing with more support.
It doesn't matter whether you teach musical theater, gospel, pop or some other genre when you veer away from the traditional choral art for a few weeks as long as you are passionate about it and are able to convey that passion to your students. Middle School students respond well to structure, but they also need a bit of variety.
Hope that gets your brain cooking a little!
I had trouble recruiting in the early years because I was all work/no play and way too technical with my daily teaching. Once I tapped into some of the ideas above, my program grew exponentially. I now teach over 300 students daily who volunteer to take my classes as part of their daily course load. Middle School students are incredibly loyal when you treat them respectfully, and know you care about them and work hard for them. I can't imagine teaching any other age group, and I am about to finish my 21st year doing it!