It’s always a struggle for band directors to include music theory in their day-to-day curriculum, but it’s important to include it when you can. One suggestion I have is to try to keep what you teach about theory as relevant to the music your students are playing as possible. This is obviously easier said than done, for your average middle school band student simply won’t know enough to do a full harmonic analysis of their LGPE pieces, but you can still explain how the scales you’re working on are used in said music. It also possible to get into differences between major and minor triads as they are used in the literature you choose. For my private saxophone students, I make a point to try to use proper terminology when possible. When teaching major scales, I start introducing terms such as tonic and dominant, and stay consistent with their use.
I had some theory knowledge going into undergrad, and I absolutely fell in love with my freshman and sophomore music theory classes. I was learning the vocabulary and techniques to explain and recreate music that I had loved for years prior. I try to use this passion and excitement to hook students into theory by explaining that music theory “gives you the tools to explain why the things you think sound cool sound cool.” Below is a little video where I explain this. Feel free to share it with your students if you think it might help motivate them to be excited about their study of music theory.