See if you can get experience in a busy Pedi practice. It will give you good experience,and skill acquisition along with the spectrum of health care for kids/adolescents. Its fast paced and will get you up to speed on what to expect.
When you are the school nurse, you will be often referring students out to their MDs. In a school setting you often work alone, as opposed to a doctors office, but your nurse peers at other schools are a resource for you.
Lots of school nurses cover more than one school in the course of the day-
ie middle school and elementary so you need to interact with many age groups.
Check to see if your state requires a school nurse certification (a state certificate as opposed to professional one.)
If so, start the courses.
See if you can shadow a few school nurses in your area for the specific skills and requirements.
Good luck and keep us posted...