I was our district's "float" nurse and had the opportunity to work at every level. First of all, the odds of getting a job in an elementary school are greater just because of the numbers of schools
. Aside from that, I think it is a good idea to start with the elementary schools because it is important to learn and understand the stages of growth/maturation. By learning this progression, you will know what information the child is missing, or should be learning.
I have settled at a wonderful elementary school and taught "Growth and Development" for the first time this spring. I had a lot to review, not only the stages of anatomy and physiology to teach about puberty, but I needed to review the stages of personality, cognitive, and moral development to understand where the children in 5th grade are expected to be. By acquiring this basic knowledge, I am better prepared to teach, and deal with, the changing and maturing student.
Especially coming from an ER, reviewing the stages of growth and development is important to you as it is for all of us, so we can have the most impact on the health and health education of our students. You may also have more experience or a preference with one age group, which is certainly an important consideration.
Good luck with finding what I think is the greatest job in the world!