Duets are wunderbar.
That's what many of us did, at just about every lesson, once we could play, even a wee bit.
A Duet book, like the one shown, is a great start.
You can have two senior students play first, then have one sit out, then a younger one sits in. Each student plays twice, one time on each part, as you rotate students.
Great for sight reading, or study first, and learn to develop dynamics etc etc.
Buy each student a book or copy the ones you think are important, and hand them out.
I always went over the chromatic scale, how we get the major scales and how we get the chords from the major scale.
We did C major, then F and G, then the students would write out all the major scales and chords on looseleaf paper.
That was accomplished on the first or second lesson. When I taught adult ed guitar, kept them busy while I tuned 40 plus guitars, and evaluated their playability.
Sent many to Ash in Brooklyn or Silver & Horland, over the bridge.