These days most of my private students are adults. A few years ago there was a healthy split between teaching adults and children the guitar. This included the days in the week I used to teach children at a school.
These days, however, I am far too busy with Guitar Domination to teach in the school and only have a couple of students under the age of 18.
In fact, the majority of my private students are over the age of 40. And this is the way I like it.