My advice? You don't really need the nurses. In my school district we had ONE nurse. That's it.
She would do the "rounds" at each school, including the junior and highschools i believe, so about 10-13 schools, arrange the shots, etc etc..but she was rarely actually around for more than a few hours every couple of weeks.
I was dx at the age of 6, was one of two diabetics at my school (by the time the older girl left, there was one younger than me). I think I saw her maybe once or twice my 6years at that school, and not even for medical reasons only because I went to the office to call my mom for whatever reason. I know my mom met with her and the principal and my teacher when I was dx (I was only two months into grade 1, and had transferred from another school in the district).
It didn't effect me at all. I got through my elementary, junior and highschool days without ever needing the nurse. As long as the adults around know what needs to happen when a kid is low and can't treat themselves it should be fine. The nurses wouldn't be doing anything those adults can't do if a kid is low or too high or needs to go to the hospital.
Obviously if there are 15 diabetics and the number is growing, the teachers should know just as much as you or the nurse on what to do.