I experienced a sudden loss this week also so I know how you all are feeling. You're in our prayers. Not sure of the ages of the school children, but I hope you have counselors at the school to talk to these children. We've never experienced a teacher passing but we have had a number of tragedies in our school the past few years where a parent(s) has suddenly died, loss of homes to fires, loss of a sibling, etc. and we've always made counselors available along with the principal speaking to each classroom individually on their level regarding these problems. We've also sent home letters to the parents as to how we're handling/dealing with these situations.
A couple of years ago we had a teacher who passed away suddenly over Christmas break. She had been teaching for almost 30 years and was greatly loved. Her family established a memorial that went for a tree and bench for the new courtyard and for books for the library (it purchased nearly 200). The PTO got a picture from the family, had it framed, small plaques engraved with her name and a dedication and it now hangs in our beautiful new media center. It's a wonderful way to remember a wonderful person who gave so much to so many children.