This problem isn't a new one but it seems that schools are facing renewed and sophisticated attempts to obtain large amounts of money through online scams.
Here is a recent example which might help you know what to look out for: A school bursar received an email apparently from the Headteacher asking for an urgent supplier payment to be made. The senders email address was ‘spoofed’ to appear genuine, and after some email correspondence regarding the transfer the Bursar went into the school during half term to establish why this payment needed to be made. The fraud was only identified by the bursar after finally reaching the Headteacher by telephone, who knew nothing of the request.
There is an increase in the volume and sophistication of such attempts which are often targeting individuals using correct names and ‘spoofed’ email addresses making the request seem extremely plausible.
If you suspect an attempt at fraud you should report it to your ISP and to Action Fraud, the National Fraud and Cyber Crime Reporting centre.