I think this is cultural. I've never ever left a voice message, and never will. I've also never received one, the few I get are robocallers not understanding no one picked up.
If you want me to pick up, send an sms explaining what it's about.
If you want me to pick up, send an sms explaining what it's about.
I rarely leave voicemails, but I will when it's urgent.
tl;dr: leave message+number, how you do so is up to you
The proper procedure is for the nurse to leave a voicemail with their school-provided contact number (either the school office or a way to dial them directly that isn't their personal number).