Fiddling expenses is currently common across the public sector. We had the MP expenses scandal but expenses claimed by civil servants, councillors, senior NHS staff or senior teachers have never been looked at.
There is also a lot of completely honest finanical mismanagement. Schools often do not understand the contacts the sign. IT is a good example where schools gets poor value for money.
No one is who works in a school would dare to be a whistleblower. Headteachers are very effective at ruining an innocent person's career.