What should I do or not do about misappropriation of funds at my school?

OK. In a nutshell: My only involvement is that as a parent volunteer I helped kids do work that a donator was willing to pay the school for a specific need. An official bank account was established (not by me, but by school representatives) earmarked for that one specific need fund, then a check was written from that donator paying the kids for their work, and the check was specifically written to that account for the one specific need we were raising $ for. I never saw or handled the check, just knew how much it was to be for. Thereafter, unbeknownst to myself or anyone involved in that fundraiser, some 'Matilda' at the school took that check the donator had written to that specific account and deposited it instead into a totally different school account and spent the $. Now, the $ was spent on good things for the kids/school, but was not deposited or spent on the specific need we had raised the $ for. This happened with 2 separate checks. No one involved with establishing the specific need fund bank account ever signed over the checks to the school fund. Now, a year later when I ask how much we have now in our specific need fund, I hear only a fraction of the amount I expect. So I question it and I am publicly accused of having "redirected" some of the $. The accusation comes from the individual whom I believe is the 'Matilda' I was able to get copies of the cancelled checks to prove the account differences (written to one name, deposited by another separate, with no endorsement). Here's what I face: the Matilda, in my book, is guilty of misappropriation/theft, for that matter slander (but that's the least of my concern). I know the kids still got a good thing from the $ and it didn't go into a personal pocket. If I press the misappropriation charges, that's a felony and the Matilda will likely lose her job. Further, an accomplice of hers (who must have handled the check as well) is a big-time volunteer at the school and no one wants to step into her shoes to take over all her doings (including me). Do I shut up and keep working to get more $ into our fund or do I report this and let them get their medicine, regardless the distractions it will bring to the school with losing a staff member and the volunteer's time and energies? In other words, do I teach kids that you can commit a felony and slander and get away with it as long as you meant well or do I shake up this community to have the felons hauled away but ultimately sleep at night?