So a few things to consider:
many districts do not advance on the salary guide with time spent in the hospital in mind. Meaning that if you had worked for 3 years as a school nurse and decided to change districts, you could expect to begin at a district as a step 3 or higher. If all you've had is hospital experience, it doesn't translate the same, and in some districts not at all.
This may be a good argument for going to work for a private school, but those positions are not generally pensioned.
As far as retirement, again it has a lot to do with the state. The pension system allows teaching staff (which the nurse is considered here in NJ) to retire anywhere from 55-65, but it depends on which tier you're in. All new employees into the pension I believe are tier 5, which required 30 years and retirement after 65 (I think... I'm tier one, so my rules are different.) Anyway you slice it, you'd have to get 10 years paid in to be vested. You could technically retire after that if you have met the age requirement.